FI67718B - POLYVINYL ALCOHOL / MELAMINFORMALDEHYD REACTION PRODUCT FOR OIL FAR OIL FOR FRAMSTAELLNING - Google Patents

Description

ANNOUNCEMENT CH H A Q

[B] (11) UTLÄGGNINGSSKRIFT 6771 8 C (45) r "i :: v'- 'V"' D '--5 1- 5 (51) Kv.lk.4 / lnt.Cl.4 c 08 G 81/02, D 21 H 3/36 SUOMI-FINLAND (21> Patent application - Patentansökning 8 0 2 0 61 (22) Filing date - Ansökningsdag 27.06.80 ^ ^ (23) Starting date - Giltighetsdag 27-06.80 (41) Made public - Blivit offentlig 28.12.80

National Board of Patents and Registration Date of display and publication

Patent and Registration Office 'Ansökan utlagd och utl.skrlften publicerad 31 .01 .85 (32) (33) (31) Privilege claimed — Begird priority 27.06.79 16.05.80 USA (US) 052928, 1A7057 (71) E.l. du Pont de Nemours and Company, 1007 Market Street, Wilmington,

Delaware 19898, USA (US) (72) Robert Leonard Adelman, Wilmington, Delaware, USA (US) (7 * 0 Oy Kolster Ab (5 ^) Polyvinyl 1 alcohol / melamine formaldehyde reaction products and their preparation method - Polyvinyl 1 alcohol / melamine formaldehyde reaction ions-produkter och förfarande för deras framstälIning

The present invention relates to a stable aqueous polyvinyl alcohol / melamine formaldehyde resin reaction product used to improve the wet strength, dry strength and other properties of products derived from fibrous cellulosic material. The invention also relates to the preparation of these reaction products.

There are numerous commercial paper machine wet end additives used in papermaking today. These have many limitations. Some examples of the most commonly used additives are as follows.

Cationic starches are often used to improve the stability of fines, fillers and pigments in cellulose and also to increase the dry strength of the resulting paper. However, such improvements are generally modest and concomitant use of cationic starch can lead to behavioral irregularities (deterioration of batch reproducibility, low solution stability, low wet strength), immiscibility with other components in the paper raw material (alum, glue, other salts) and biological oxygen demand (BOD) for an additive that is not in the pulp or is recycled and enters wastewater.

Other wet-end additives are often used to impart permanent wet strength to the resulting paper, such as cationic urea-formaldehyde (UF) resins, amine-containing polyamides treated with epoxides (e.g., Hercules' Kymene "557), or melamine-formaldehyde (MF ) resins (e.g. "Prez" 607, American Cyanamid) .However, UF resins are slowly vulcanized by machine, while polyamides are relatively expensive, slow to adsorb to their cellulosic pulp, and make it relatively difficult to re-encapsulate paper.FM resins show poor pigment retention and fill and also have low water absorption capacity, while absorption capacity is often desirable in combination with wet strength.All these types of additives provide only a modest dry strength improvement.Also, none of the above types are currently recognized as wet tissue strength enhancers (with their higher ease of use), which would allow VAT and, in some cases, improved production capacity.

Conventional soluble polyvinyl alcohol in the form of powder, granules or crushed fiber has been used in Japan as an additive in the wet end of a paper machine. Improved paper strength and oil resistance were observed. However, careful control of the particle size, preliminary heat treatment, and degree of hydrolysis of the polyvinyl alcohol is required. Careful control of the temperature and water level of the particles and the paper formed is also required before it is passed through the drying rollers (see "Polyvinyl Alcohol", edited by C.A. Finch, Wiley, N.Y. (1973), pages 301-305). Because these particles are nonionic, low stability of the fines would be expected, and because they do not vulcanize, they do not have wet strength capacity.

The use of melamine-formaldehyde resins as wet-end additives for high-strength papers is well known (see C.S. Maxwell's review in TAPPI-Monograph 6771 8 3

Well. 29, "Wet Strength in Paper and Paperboard; edited by J.P. Weidner (1965), pp. 20-32).

The reaction of starch and melamine-formaldehyde cationic precondensate to produce cationic starch (which promotes binder adsorption) is described in U.S. Patent No. 2998344 (cf. column 3). No concentration effects were mentioned as important. The product was also unsatisfactory as a binder for cellulosic pulp (cf. column 6).

U.S. Patent 3,594,271 describes acidic colloidal aqueous solutions of a cationic reaction product of a cationic thermoplastic melamine-formaldehyde acid colloid with 5-50 times the weight of water-soluble starch and a process for treating paper therewith. Such products have been described to provide good adsorption to fibers and improved dry strength combined with low wet strength. The total dry matter content of the mixture is 2-10%, but it is mentioned that "this is not critical" (column 2). . It was also mentioned that the low wet strength is the result of the low content of melamine-formaldehyde resin compared to starch.

U.S. Patent 3,424,650 discloses that starch reacted with formaldehyde-guanidine-melamine resins was made much more adsorbable to cellulosic fibers. The addition of all three materials as reagents in ratios of 9-14 / 0.4-1.6 / 0.4-1.6 in the same order was critical to produce a relatively stable resin and to provide sufficient activity to improve the dry strength of paper products by prior reaction with starch. The concentration of the reagents can also be from 1 to 40% by weight.

A combination of guanidine-formaldehyde resin and a hydrocolloid (such as starch or polyvinyl alcohol) in a weight ratio of about 2/1 is disclosed in U.S. Patent 3,002,881 as a good wet end additive that increases the wet strength of the resulting paper. It is likely that the components will be added independently to the dilute pulp slurry. There is no mention of the pre-reaction of resin and polyvinyl alcohol due to the lack of stability of the premixes (cf. column 5).

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Other methods for preparing cationic highly adsorbable polyvinyl alcohols have also been described. However, these would have higher costs and / or problems with a toxic reagent. These include the following: U.S. Patent Nos. 3,597,313 and 3,772,407 describe copolymers of vinyl alcohol modified with cationic monomers.

U.S. Patent 3,051,691 discloses that polyvinyl alcohol and calcium cyanamide form cationic polymeric polyols that can replace cellulose.

The use of polyvinyl alcohol plus methylol melamines (monomeric melamine-formaldehyde) in paper coatings is described in GB 551 950. The use as a textile finishing agent is described in U.S. Pat. No. 2,876,136. . The described polyvinyl alcohol / methylol compound ratio ranged from 1/1 to 1/125.

U.S. Patent 3,067,160 described that even the addition of small amounts of polyvinyl alcohol to cationic melamine formaldehyde resin acid colloids (methyl ether form) was unsuccessful. Such systems were highly unstable and gelled, thus indicating that stable melamine-formaldehyde acid colloidal solutions containing polyvinyl alcohol could not be expected.

It has long been known that the addition of a crosslinking agent in moderate or high concentrations to polyvinyl alcohol results in the formation of a gel, but if the solution is sufficiently dilute, almost exclusively intramolecular reactions occur so that no gel is formed (cf. W. Kuhn and G. Balmer,

Journal of Polymer Science Vol 57, pages 311-319 (1969). Furthermore, the work of these researchers shows that the reaction of polyvinyl alcohol with a degree of polymerization of the order of 1000-2000 with a highly functional crosslinking agent such as melamine-formaldehyde acid colloid (and the latter concentration is up to 20-100% by weight of PVA) has a very low PVA content. must be present (approximately 0.3-0.5%) to prevent gelation. Thus, it is surprising that the reaction between PVA and MF resin acid colloid can take place at solution concentrations of up to 3.75% and stable and still active systems are obtained even when the solution is heated vigorously.

These researchers state that complete separation of the polymer chains is necessary for this dilution effect to occur.

Other researchers have also reported that complete separations of polyvinyl alcohol molecules require concentrations of less than 0.25% and that if the concentration is increased to about 0.9%, the expanded polymer coils will have to penetrate each other and the entanglements will become quite significant (cf. " Polyvinyl alcohol ", JG Pritchard, Gorden and Breach, NYD, (1979) page 15).

The polyvinyl alcohol / melamine formaldehyde resin reaction product of the present invention is characterized in that it consists of a polyvinyl alcohol polymer and an acid calloid of a cationic melamine formaldehyde resin. , ranging from about 0.7% by weight to a level that does not cause gelling in a non-draining state under gravity in 48 hours, but not more than 5% by weight, wherein the logarithmic viscosity number of the polyvinyl alcohol polymer used is about 0.3-1.4 dl / g measured in water at 30 ° C at a concentration of 0.5 g / dl, and wherein the polyvinyl alcohol / melamine formaldehyde resin reaction product may further contain up to about 6 parts by weight of starch which is unmodified, modified or decomposed starch or starch derivative per part by weight of polyvinyl alcohol.

The products of the invention can improve the wet strength, dry strength and other properties of a product derived from fibrous cellulosic materials, e.g. paper, by treating fibrous cellulosic materials or pulp with the products of this invention.

As used herein, the word "stable" in the context of a stable aqueous polyvinyl alcohol / melamine formaldehyde resin reaction product means that gelation to a non-draining state by gravity does not occur within 48 hours.

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Contrary to the above prior art publications, and very surprisingly, it has been found that mixtures of polyvinyl alcohol and cationic melamine-formaldehyde-resin acid-colloid can react with each other at concentrations of up to about 3% and higher up to 85-90 ° C. at temperatures of 1 to 2 hours, if desired, without leading to significant amounts of gel or success of the adsorption activity of the reaction product relative to cellulose. This finding makes the application of the reaction between polyvinyl alcohol and melamrine-formaldehyde commercially possible because these concentrations and reaction rates allow the use of equipment already used for cationic starch solutions added on a paper machine to achieve improved properties.

The limitations of the prior art wet surfactants described above are reduced by using the polyvinyl alcohol / melamine-formaldehyde resin reaction products of this invention. Improvements over cationic starches are seen in batch reproducibility, high solution stability, high wet tissue strength, better compatibility with other components in the paper raw material (salts, glue, fillers), lower BOD (biological oxygen demand), better persistence of fines and higher persistence of fines. dry strength and wet strength and toughness of the resulting paper. In terms of wet strength agents, the improvement over urea / formaldehyde resins shows a high vulcanization rate on the machine. The advantage over melamine-formaldehyde resins is shown by the higher water absorption rate of the resulting paper (in non-adhesive blends), the better stability of the fine parts and the higher wet toughness. Advantages over nonionic polyvinyl alcohols as a wet additive include easier process control, better stability of fines, and better sheet properties such as the wet strength properties of the paper. The wet strength properties and process advantages mentioned above show an improvement over the use of the second cationic polyvinyl alcohol.

Thus, certain reaction products of polyvinyl alcohol and a cationic melamine-formaldehyde resin acid colloid are provided which are highly adsorbable to the cellulose pulp and as such are remarkably suitable for use in the paper industry. These products are capable of forming water - resistant products when dried and yet have good solution stability up to a solution concentration of about 3.75% by weight and even higher. These reaction products can be prepared more easily and at lower cost to the customer than the highly adsorbed polyvinyl alcohols described previously.

However, they really require quite special conditions in their manufacture to obtain products with improved properties compared to other wet end additives going into the papermaking process. The improved solution stability, high cellulose pulp adsorption capacity, improved processing ability and control properties, and improved paper properties make the products of this invention particularly suitable for use at the wet end of a paper machine, also allowing for lower overall paper machine costs.

The polyvinyl alcohol polymer component of the product of this invention may be of a "fully" hydrolyzed grade (99.0 to about 100 mol% hydrolysis of acetate groups), a partially hydrolyzed grade (80-90% hydrolysis), a polymer having moderate hydrolysis, or mixtures thereof. . Fully hydrolyzed grades as well as higher molecular weight commercial grades are recommended when it is desired to obtain papers with the highest wet strength properties. The degree of polymerization of the polyvinyl alcohol should be about 600 to 3000, which is reflected in logarithmic viscosity numbers inn.) Of about 0.3-1.4 dl / g. The logarithmic viscosity number is measured in water at 30 ° C at a concentration of 0.5 g / dl. For many commercial grades of polyvinyl alcohol, this corresponds approximately to a solution viscosity (4% aqueous solution, 20 ° C, Hoppler's falling ball method) of about 4-160 cP with values of about 10-70 cP being preferred.

The polyvinyl alcohol component of this invention may also be a copolymer of vinyl alcohol, such as that obtained by hydrolyzing a vinyl acetate copolymer with small amounts (up to about 15 mol%) of other monomers. Suitable comonomers 6771 8 are, for example, esters of acrylic acid, methacrylic acid, maleic or fumaric acids, itaconic acid, etc. Also copolymerization of vinyl acetate with hydrocarbons, e.g., α-olefins such as ethylene, propylene, or octadecene, etc., with higher vinyl esters such as vinyl butyrate, 2-ethylhexoate, stearate, trimethylacetate (or their homologous acetate). 10 "type sold by Shell Chem. Co.), etc. provides copolymers that can be hydrolyzed to suitable polyvinyl alcohol copolymers. Other suitable comonomers include N-substituted acrylamides, vinyl fluoride, allyl acetate, allyl alcohol, etc. Free unsaturated acids such as acrylic acid, methacrylic acid, monomethyl maleate, etc.

Another major component, the cationic melamine-formaldehyde-resin acid colloid, is a colloidal solution of a low molecular weight polymer (molecular weight ca. 1700) obtained when trimethyl-limelamine (TMM) (or slightly polymerized TMM, supplied by certain suppliers as easily soluble in water). , such as "Cezamid 607" from American Cyanamid Corporation) is dissolved in water containing hydrochloric acid (about 0.8 moles of HCl per mole of TMM) and aged at room temperature for at least one hour. These colloidal particles are positively charged (cationic) and are known to adsorb irreversibly even at very low concentrations to negatively charged cellulosic fibers. These are called "genuine" colloids.

A detailed description of melamine-formaldehyde resin acid colloids is given in TAPPI Monograph Series No. 29, "Wet Strength in Paper and Paperboard" (John Weidner, editor. Tech. Assoc., Of the Pulp and Paper Industry, NYC, (1965), pp. 20-32). Included in this specification and suitable for use in the products of this invention are so-called "high power" melamine colloids in which 1-7 moles of additional formaldehyde per mole of TMM have been added to TMM and the optimum HCl / TMM molar ratio has been calculated to be about 0.8. from about 0.6. For maximum efficiency 9 6771 8 "high power" colloids are recommended. Some advantage has also been observed in the properties of the final paper when the "high power" melamine-formaldehyde colloid is prepared by dissolving TMM in cold water and then adding acid. The preparation of the melamine-form-aldehyde component by this "cold" procedure is described below.

To avoid poor solution and bonding properties, polyvinyl alcohol should not be present in solution during the preparation of the melamine-formaldehyde resin acid colloid.

In the production of the "high power" type of cationic melamine-formaldehyde resin acid colloid, aldehydes other than formaldehyde may be added during the maturation process of the colloid. These aldehydes may have up to about ten carbon atoms. Concentrations may be from 8 to 100% by weight based on the weight of trimethylol melamine. Types of aldehydes that can be used include simple homologues of formaldehyde, including branched chain types. Examples are acetaldehyde, propionaldehyde, butyraldehyde or 2-ethylhexylaldehyde. Acetaldehyde is particularly effective, especially at lower concentrations (see e.g. 14). Also useful are substituted aldehydes such as phenylacetaldehyde, chloroacetaldehyde, 3-methoxypropionaldehyde, aldol and crotonaldehyde. Polyaldehydes that can be used include glutaraldehyde, glyoxal, adipaldehyde, and terephthalaldehyde. Glutaraldehyde is particularly useful (see, e.g., 15) in providing adsorption values for unusually high filler stability, Scott internal bond strength, and wet tensile energy.

The optimum HCl / TMM molar ratio for the addition of higher aldehydes is closer to 0.8 than 0.6.

Other components may also be present during the reaction of the polyvinyl alcohol and melamine / formaldehyde resin acid colloid, which components may act as extenders in reducing costs while not reducing certain properties such as pigment stability. These include unmodified starches, degraded (acid-modified, enzymatically modified) starches, modified starches such as hypochlorite oxidized starch, or starch derivatives such as hydroxy-T-10 6771 8 ethyl starch or cationic starch. The amount of starch that can be added can be up to about 6 parts by weight of the above-mentioned starch per 1 part by weight of polyvinyl alcohol to form, for example, a starch / polyvinyl alcohol / melamine-formaldehyde reaction product in a ratio of & 71/1 and still provide a slight improvement in starch / melamine. compared to formaldehyde reaction products. See, for example, Tables XI and XII in Examples 13, which show the advantage of 3/1/1 starch / polyvinyl alcohol / melamine-formaldehyde over 3/1 starch / melamine-formaldehyde.

The weight ratio of polyvinyl alcohol to melamine-formaldehyde resin, based on dry weight, can be about 1 / 1-5 / 1.

Higher ratios result in a low level of adsorption in the pulp.

On the other hand, too low a ratio results in a brittle product, which is reflected in the deteriorating physical properties of the resulting paper.

The polyvinyl alcohol and melamine-formaldehyde resin acid colloid can be reacted by stirring the aqueous solutions of each together for several hours at room temperature or by heating (30-90 ° C for about 3-15 minutes) or by slurrying the polyvinyl alcohol powder or granules by mixing melamine-formaldehyde acid with melamine-formaldehyde acid. at about 80-95 ° C until the polyvinyl alcohol is dissolved. However, it is important in all modifications that the total dry matter content after mixing is about 0.7-3.75% by weight or even higher up to a level that does not cause gelling in the non-draining state by gravity, but not more than 6% by weight. At higher concentrations, the viscosity of the mixture rises faster than is likely to be useful and leads to gel formation. At a dry matter content of 8%, gelation could follow in a few minutes and at a concentration of 5%, depending on how favorable the other conditions are, gelation may or may not occur in about H8 hours. The total dry matter content should preferably be between about 2-3% by weight.

One of the most economical ways to prepare the product is as follows: Trimethylol melamine is dissolved in water and hydrochloric acid and matured into an oligomer at room temperature in an acid-proof container. It is then pumped into a second tank (reaction vessel) where it is diluted with water to a concentration of about 0.6% by weight. In the third tank, the polyvinyl alcohol is dissolved with heating and stirring to give a 10% by weight solution. This is then pumped hot into a reaction vessel (containing a melamine-formaldehyde resin acid colloid) and the mixture is gently stirred to form the final product. It is recommended to use a ratio of alcohol to melamine-formaldehyde in the product of about 2 / 1-3 / 1 and a total dry matter content of about 2% by weight. The temperature of the reaction mixture is then about 33 ° C, which is high enough to guarantee the formation of the product within a stirring time of about 15 minutes. The mixing temperature can be ambient temperature (approx. 20 ° C) if a mixing time of approx. 24 hours is allowed.

An alternative route to the reaction product is, as mentioned above, to add the powdered polyvinyl alcohol directly to the diluted melamine-formaldehyde resin acid colloid in a reaction vessel. to form a slurry and then heat to about 85-90 ° C for 0.25-2 hours or until the polyvinyl alcohol is dissolved. The advantages of this route are that the polyvinyl alcohol dissolves rapidly in such a medium (about 15 minutes) and a third tank is not required. The disadvantage of the latter method is that more energy is required to heat a larger volume of solution.

The products obtained from both procedures are storage stable (in terms of viscosity and activity) for at least three weeks. No change in solution viscosity pathway has been observed in several cases for more than three months.

Mixtures of certain solid grades of polyvinyl alcohol in powder or granular form with solid condensation products of melamine and 3 moles of formaldehyde soluble in water or an aqueous solution of an acid can also be used, e.g. by applying a slurry procedure. The dry mixture may be added to water or an aqueous solution of the acid and, if desired, additional formaldehyde, preferably cold, to dissolve the melamine-formaldehyde condensation products and convert them to a cationic rosin acid colloid while maintaining the substantially insoluble form of polyvinyl alcohol. Thereafter, by adding an appropriate amount of water to finally obtain a solution containing about 0.7-6% dry matter, the slurry is heated as above to cause the polyvinyl alcohol to dissolve and react. The ratio of polyvinyl alcohol to melamine-formaldehyde resin acid colloid may be about 5 / 1-1 / 1 by weight. The polyvinyl alcohol used should contain as little cold water-soluble matter as possible; a quality with a maximum cold water solubility of about 8% by weight might be acceptable, while a quality of no more than about 4.5% by weight would be recommended. A maximum cold water soluble content of about 2% by weight is desirable. The melamine-formaldehyde resin acid colloid should be prepared under milder conditions than in the previous procedures, such as using a higher dilution to prevent gelation: 9% by weight instead of the usual 14-18% by weight dry matter concentration gave good results.

The structure of the polyvinyl alcohol / melamine-formaldehyde reaction products of this invention has not been precisely determined.

However, the infrared spectra of the cast films showed a chemical reaction of polyvinyl alcohol and melamine-formaldehyde resin via -OH groups to form graft copolymers.

The polyvinyl alcohol / melamine-formaldehyde product is preferably used in connection with conventional methods of making paper sheets and other cellulosic products. Preferably, the reaction with the cellulosic pulp is carried out by internal addition to the cellulosic pulp before forming the paper sheet. Thus, an aqueous solution of the reaction product may be added to the aqueous suspension of paper raw material while the latter is a flat wire machine in a suction box, vane pump, feedstock chamber, hydropulper, or some other process location prior to the sheeting site. The high rate of adsorption of the polyvinyl alcohol / melamine-formaldehyde reaction product with the pulp allows many choices in this regard. Many different pulps that can be effectively treated include bleached and unbleached sulphate pulp (kraft pulp), bleached and unbleached sulphite pulp, soda pulp, neutral sulphite pulp, semi-chemical pulp, pulp pulp or mixtures of these fibers. In addition, fibers of viscose ion, 6771 8 13 glass, regenerated cellulose, polyamide, polyester or polyvinyl alcohol can also be used in connection with cellulose pulp. The recommended pH range of the pulp feedstock containing the polyvinyl alcohol / melamine-formaldehyde reaction product is about 5-8; this range indicating good adsorption and filler stability. The best wet strength properties of the resulting paper occur in the pH range of about 4-6.5.

Materials that could be added to the slurry together with the polyvinyl alcohol / methylamine-formaldehyde reaction product include cationic surfactants, cationic urea-formaldehyde resins or cationic polyacrylamides. Polymers derived from polyamides containing amino groups along the polymer backbone and reacted with epichlorohydrin (such as Hercym's "Kymene" 557) can also be added.Anionic polyacrylamide polymers, reinforced resin adhesives, fillers, pigments, alum, etc. may also be present. .

The sheet is formed, pressed and then dried by conventional means. The latter step operates the volcanic polyvinyl alcohol / melamine-formaldehyde reaction product in its water inert state. Good runnability and good paper formation have been demonstrated.

The amount of polyvinyl alcohol / melamine-formaldehyde reaction product added to the pulp slurry varies between about 0.02-10% based on the dry weight of the pulp. The recommended range is about 0.05-3% and depends on the properties, pulp type and current conditions of use of the final paper product. Thus, too little polyvinyl alcohol / melamine-formaldehyde in the slurry gives too little improvement in properties to be interesting. Too much polyvinyl alcohol / melamine-formaldehyde could be uneconomical.

The following examples illustrate the invention. All parts and percentages and ratios are by weight unless otherwise indicated.

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Preparation of helamine-formaldehyde-resin acid colloids

Example A

A "high power" melamine-formaldehyde resin acid colloid was prepared by adding 13.2 g of reagent grade concentrated hydrochloric acid to 365 g of distilled water. Then, 50 g of trimethylol melamine powder was added with stirring, followed by 95 g of a 37% aqueous formaldehyde solution. After slow stirring overnight at room temperature, the expected blue veil appeared. The acid colloid was diluted with 365 g of distilled water to give a dry matter content of 7.4% (determined by drying in a convection oven at 110 ° C for 1 hour). This is about 74% of theory if no formaldehyde is lost during the drying process. The above initial ratios give 0.6 mol HCl / mol trimethylol melamine and 5 mol formaldehyde / mol trimethylol melamine. The addition of a drop of concentrated HCl to a few milliliters of acid colloid resulted in immediate coagulation as expected if the melamine-formaldehyde acid colloid was sufficiently aged. The pH of the colloid was 1.8. The stability of the acid colloid was excellent for at least a month.

Example B

An alternative method for preparing melamine-formaldehyde resin acid colloids is as follows. Reagent-grade concentrated HCl (11.6 g) was added to 346 g of distilled water. 43.2 g of commercial spray-dried trimethylol melamine ("Parez" 607, manufactured by American Cyanamid Corporation) was then added with stirring. The solution was stirred slowly overnight at room temperature. The acid colloid was diluted with 346 g of distilled water to give a colloidal dispersion containing 5.70% dry matter, the HCl / TMM molar ratio was 0.6 / 1.0.

Example C

Another alternative preparation of melamine-formaldehyde resin acid colloid is shown below. Reagent grade concentrated HCl (15.8 g) was added to 390 g of distilled H 2 O. 43.2 g of "Parez" 607 were then slowly added with stirring. The solution was then stirred overnight at room temperature. The acid colloid was diluted with 340 g of distilled water to give a colloidal dispersion containing 6.6% 6771 8 dry matter. The molar ratio HCl / TMM was 0.8 / 1.0.

Example D

A "cold" procedure for preparing a melamine-formaldehyde-resin acid colloid is described below. The ratios of the components are the same as in Example A. To 150 g of distilled water cooled to 14 ° C in an ice bath was added 25 g of trimethylolmelamine with stirring. 47.5 g of 37% formaldehyde were then added and 6.5 g of concentrated HCl in 32.5 g of distilled water were added to the suspension. After stirring for several hours, the suspension became a milky solution. The temperature was allowed to rise to ambient temperature overnight with slow stirring and the solution was then diluted with 182 g of distilled water. The dry matter percentage was 6.9%.

Manufacture of polyvinyl alcohol / melamine-formaldehyde interactions

Example 1 This example describes a "slurry technique". To 10.4 g of a "high power" type melamine-formaldehyde resin acid colloid (7.2% dry matter, prepared according to the method of Example A) was added 96 g of distilled water with slow stirring at room temperature. To the above was added with stirring 1.5 g of a medium molecular weight, fully hydrolyzed grade commercial polyvinyl alcohol powder having a viscosity as a 4% aqueous solution at 10 ° C of 30 mPa * s (30 cP) with about 1% acetate groups and of which more than 99.0% passed through No. 10. The slurry was then heated with stirring to 85-96 ° C for 15 minutes at which time the polyvinyl alcohol appeared to be completely dissolved. The clear solution of the product was cooled to room temperature. The pH was about 2.8, the dry matter content was 2.0% and the solution viscosity was low (Brookfield less than 1 cP). The polyvinyl alcohol / melamine formaldehyde resin ratio was 2/1. When products of this type were tested at a total dry matter content of 12%, they failed (gelled in a few minutes), also failed at a dry matter content of 4% (gelled in less than 16 hours), but were stable at a dry matter content of 2.9%. matter content.

ΐ ____ 16 6771 8

Example 2 This example is similar to Example 1 except that a melamine-formaldehyde resin acid colloid prepared according to the method of Example B is used.

The run was essentially successful in this case with a total dry matter content of up to 5% (although the viscosity actually increased to about 3.2 cP after 48 hours and traces of gel were visible). The adsorption efficiency to bleached cellulose pulp at pH 4.0 was greater than 73% (compared to about 18% with polyvinyl alcohol alone).

Example 3 This example is similar to Example 1 except that a melamine-formaldehyde resin acid colloid prepared according to the method of Example D is used.

Successful products were obtained at the 2% level and 2.7% dry matter content, but failed at the 6% dry matter content (gelled in 16 hours) but were stable at the 2.9% dry matter content.

Example 4 To a 250 ml Erlenmeyer flask containing a magnetic stir bar was added 55.6 g of a 4.05% aqueous solution of the polyvinyl alcohol used in Example 1. To this solution was added, with stirring at room temperature, 10.5 g of melamine-formaldehyde resin acid colloid, dry matter content 7.15%, prepared according to the method of Example Q. This was followed by 84 g of distilled water and the temperature was then raised to 65 ° C for 15 minutes. An active, stable product was obtained, the polyvinyl alcohol / melamine-formaldehyde weight ratio was 3/1 and the dry matter content of the solution was 1.9%.

Similar successful examples were run with other grades of polyvinyl alcohol, different melamine-formaldehyde resin acid colloids, polyvinyl alcohol copolymers with different polyvinyl alcohol / melamine-formaldehyde ratios, and in the presence of corn starch or potato starch. The addition of a hot concentrated (10%) polyvinyl alcohol solution to the diluted (0.6%) melamine-formaldehyde resin acid collage was also successful. In fact, this is one of the preferred methods for preparing the polyvinyl alcohol / melamine-formaldehyde-resin reaction products of this invention.

Comparative Example 1

A 10.1% solution (66.6 g) of the polyvinyl alcohol used in Example 1 was mixed with 7.2% melamine-formaldehyde-resin acid colloid ("high power" type) (31.2 g) together with 2.2 g of distilled water at room temperature to give a polyvinyl alcohol / melamine-formaldehyde mixture in a ratio of 3/1 with a total dry matter content of 8.7%. The viscosity of the "solution" increased rapidly; 6.3 off (measured with Gardner Holdt calibrated viscosity tubes) after stirring for about one minute to over 148 off after 30 minutes to form a hard gel.

Comparative Example 2 To 37.2 g of 7.2% melamine-formaldehyde resin acid colloid ("high power" type) was added 158 g of water and then, with stirring, 5.36 g of the polyvinyl alcohol powder used in Example 1. The ratio between polyvinyl alcohol and melamine formaldehyde was 2/1 and the dry matter content of the product in solution was 4%. The slurry was then heated to 85 ° C with stirring. The result was a gel in less than 16 hours.

Comparative Example 3

To a solution of 4.4 g of medium molecular weight, fully hydrolyzed grade commercial polyvinyl alcohol (having a viscosity of 14 mPa · s (cP) as a 4% aqueous solution at 20 ° C and about 1% acetate groups) in 100 ml of water was added 1 g of "Parez" 607-TMM with stirring. The TMM dissolved slowly. The pH was then lowered by adding 2.9 g of concentrated HCl. After stirring for 16 hours at room temperature, a colloidal solution was obtained. The activity of the product was very low (adsorption efficiency to cellulose pulp was only 8% at pH 4.5).

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Example 5

As suggested above, the reaction between polyvinyl alcohol and melamine-formaldehyde resin acid colloid to form a new product shows: (1) a significant increase in viscosity when the components are mixed together at somewhat higher concentrations than within the scope of this invention, but otherwise under the same or even milder reaction conditions; (2) a significant increase in the adsorption efficiency relative to the cellulose pulp compared to that obtained when polyvinyl alcohol alone is used, indicating polyvinyl alcohol having cationic groups. This is shown in Table I.

Table I

Additive added to the mass Adsorption composition of the additive _ centimeter to the mass PVA 2 7 3/1 PVA / MF (HE) 69 2/1 PVA / MF (HE) 94 MF (HE) 89

Cationic starch 32 (a) All used in a concentration of 1,6%, calculated on the dry mass. Polyvinyl alcohol was used in Example 1. MF (HE) was a melamine formaldehyde resin acid colloid, of the "high power" type. The cationic starch was "Cato" 15 (National Starch).

(b) The pulp was unbleached Western kraft pulp, Canadian Standard Grinding Rate (CSF) 600. The consistency of the ground raw material in the slurry was 2.5%. The initial concentration of the additive in the aqueous phase was 0.041%. The gravimetric procedure was used to determine the concentration of the additive in the filtrate after exposure to the pulp. The pH of the pulp was 4.5 except in the case of polyvinyl alcohol alone, where it was 6.5.

It can be seen from Table I that the level of adsorption of polyvinyl alcohol / melamine-formaldehyde "high power" reaction products to the pulp is much higher than with polyvinyl substituents alone or even with commercial cationic starch.

6771 8 19 (3) The spray results also show the reaction between polyvinyl alcohol and melamine-formaldehyde resin acid colloid, (a) The solutions gave colored reaction products with boronic acid iodine, such as polyvinyl alcohol alone. However, the intensity of the complex was lower than would be expected from polyvinyl alcohol alone, (b). In the infrared spectra of the air-dried cast films at room temperature, the 1000 cm -1 peak of the melamine-formaldehyde resin acid colloid has disappeared, suggesting that most of the methylol groups have reacted. The absorption of polyvinyl alcohol at about 830 cm on the -OH bond is also reduced, suggesting some kind of reaction with these groups.

Example 6

Increased adsorption efficiency compared to polyvinyl alcohol alone and increased adsorption rate compared to commercial cationic wet-end additives (such as "Kymene" 557, presumably cationic polyamide containing bleached northern softwood sulfite / bleached northern hardwood pulp) under other conditions the same as in Example 5. The results are summarized in Table II. Thus, the polyvinyl alcohol / melamine-formaldehyde interaction product in a ratio of 3/1 has an adsorption efficiency of about 80% after 15 minutes of exposure to wet pulp, while polyvinyl alcohol alone has only 18%. Furthermore, polyvinyl alcohol / melamine-formaldehyde reached its maximum adsorption level within 1 minute, while "Kymene" 557 did not reach high adsorption levels for more than 5-10 minutes. Thus, polyvinyl alcohol / melamine-formaldehyde offers more flexibility in insertion points (vane pump, machine chamber, suction box, etc.) on a flat wire paper machine than other cationic wet-end additives.

6771 8 20

Percentage of adsorption of additive added to the mass Composition of the substance in the mass after the stated minutes of exposure 1 5 10 15 PVA 12 14 16 18 "Kymene" 557 53 68 68 77 3/1 PVA / M F (HE) 84 79 - 10

Example 7

As mentioned above, the solutions of the polyvinyl alcohol / melamine formaldehyde reaction products of this invention have excellent storage stability. Thus, no increase in viscosity or gel accumulation occurs over weeks or months and the activity remains high for at least two months with the polyvinyl alcohol / melamine-formaldehyde products of the above examples. Similarly, contrary to the properties of cationic starch solutions, no tendency for mold accumulation is observed.

These products are also heat vulcanizable on a paper machine. In other words, significant levels of permanent wet strength are achieved rapidly, clearly faster than with urea-formaldehyde resins and probably as fast as with melamine-formaldehyde resins alone. On the other hand, recovery of waste or scrap paper is faster than with melamine-formaldehyde resins by heating under very mild acidic conditions (see Example 12).

This example quantitatively demonstrates the benefits in wet tissue strength of the polyvinyl alcohol / melamine-formaldehyde reaction products of this invention. The paper was produced on a 91.4 om wide flat wire machine operating at a speed of 30.5 m / min.

The pulp was a 70/30 blend of bleached hardwood pulp / bleached softwood pulp ground to 5G0 CSF. For wet tissue studies, 5.1 cm wide strips were cut from the edge of the web with a felt roller and the breaking load at two different water contents was measured with an Instron traction machine. The breaking length (strength) was calculated and the interpolated values of the breaking length were compared with the same water contents (35% dry matter) and additive concentrations where they are normally used for dry and / or wet strength papers applications. These are shown in Table III.

6771 8 21

Table III

Additive Concentration,% Breakthrough length, Main use ___ meters__ ~ "Kymene" 557H 0.6 57 wet weight pap.

"Cato" 9 cationic 0.6 63 dry paper starch 2.0 estimated 60-65 dry paper MF resin wet paper

Not at all 3/1 PVA / KF from Example 4

It can be seen that most of these additives actually reduce wet tissue strength (presumably by interfering with the internal reactions of the cellulosic pulp). However, the polyvinyl alcohol / melamine-formaldehyde reaction product actually improves the strength of the wet tissue.

Example 8 This example shows the greater stability of the fine particles of cellulose that is possible using polyvinyl alcohol / melamine formaldehyde as an additive. Process data, achieved with high first run persistence, are recognized in the literature (K.W. Brit, Paper Trade Journal, April 15, 1977, p. 36). It is also well known that the stability of fine portions of cellulose (and also of pigment and / or filler) can be significantly lower at high shear rates found in a commercial paper mill than at low shear rates in conventional laboratory experiments. K. Britt has developed a single-screen apparatus for the determination of fines, filler, and pigment in cellulose in the laboratory under conditions approximately equivalent to the turbulence to which the pulp feedstock enters when water drains from it in the early parts of the paper machine wire. This is called a "dynamic drain can" or "Britt1 can". This is described in TAPPI Report No. 57, "Retention of Fine Solids During Paper Manufacture" (9/1/75). K.W. Britt Appendix in Chapter 8.

Following Britt's procedures, the following results summarized in Table IV were obtained for the 3/1 PVA / MF (HE) reaction product compared to two commercial cationic starches at different additive concentrations and different pH values of the pulp feedstock.

6771 8 22

Table IV

Additive Concentration _ Persistence (%) (b)

Not at all ”4'5 39 * 5 5.5 34.3 6.5 45.4

Cationic starch ^ 0.1 4.5 37.9 5.5 50.8 6.5 54.3 0.7 4.5 53.8 5 r5 51.2 6.5 54.9 2.0 4.5 39.9 5.5 48.5 6.5 49, -8 3/1 PVA / MF (d) 0.1 4.5 62.4 5.5 50 j8 6.5 46.9 0.7 4.5 61.3 5.5 53.3 6.5 45r2 2.0 4.5 84, 0 5.5 71.9 6.5 62.7

Cationic starch ^ 2.0 6.5 21.4 (a) Calculated on the dry mass (b) Calculated on the dry mass, determined in a Britt can at 1000 rpm, using western unbleached kraft paper pulp, CSF 620, tap water. The amount of finely divided parts of cellulose in this pulp is 9.3%.

(c) “Cato” 15, National Starch.

(d) Prepared by the method of Example 4.

(e) "Cato" 9, National Starch.

6771 8 23

It is evident that pH 4.5 is optimal for stability purposes with polyvinyl alcohol / melamine-formaldehyde, while pH 6.5 is perhaps best with cationic starches. It is also apparent that at optimum pH for each additive, polyvinyl alcohol / melamine-formaldehyde is better than cationic starches at all additive concentrations.

Similar advantages were demonstrated in the stability of kaolin or pigment (TiCl 4) in the unbleached kraft pulp used above and also in the bleached pulps, as shown in Tables V and VI.

Table V

Additive (concentration 2%) Stability of kaolin (%) (a)

Not at all 2

Cationic starch 15 MF (HE) resin 12 3/1 PVA / MF 28 (a) Bleached softwood sulphite pulp / bleached hardwood kraft pulp in a ratio of 50/50, CSF 500. Britt can at 1000 rpm. The cationic starch was "Cato" 9. Polyvinyl alcohol / melamine formaldehyde was prepared by the method of Example 4.

Table VI

Additive Concentration Ti0? Stability,%

Cationic starch 0.7 ^ 22 2, 0 37 MF resin 2.0 16 3/1 PVA / MF 0.7 45 2.0 58 ^ Bleached softwood sulphite pulp / bleached hardwood pulp in a ratio of 50/50, CSF 500, Britt ' in a can at a speed of 1000 rpm. Additive concentration calculated from the mass.

6771 8 24

The cationic starch was "Cato" 9. PVA / MF was prepared by the method of Example 4.

In order to show that these high values of the stability of the fines were not associated with coagulation, which could impair the properties or process properties of the paper, the optical properties of the obtained paper were examined and found to be excellent. This is described below in Example 9.

The following examples illustrate improved paper and paper-based products that can be obtained by using polyvinyl alcohol / methylamine-formaldehyde reaction products as additives to a paper machine.

Example 9 Using paper prepared on a flat wire machine f as described in Example 7, the scattering constant was determined as in TAPPI method 218-05-69 to determine reflectance, then using the data in TAPPI method 425-05-75 for SW values, dividing by the basis weight and multiplying by 10 000 to give values of 2 in cm / g. The results are given in Table VII for paper containing 10% kaolin.

Table VII

2 (a)

Additive Concentration% Scattering constant (cm / g)

Not at all - 395 "Cato" 9 0.6 409 2.0 420 "Cato" 15 0.6 416 2.0 382 MF (HE) 0.6 408 2.0 420 3/1 PVA / MF 0, 6 472 2.0 450 (a) Bleached hardwood kraft pulp / bleached softwood kraft pulp in the ratio 70/30, CSF 500, the concentration is calculated from the dry pulp. PVA / MF was prepared by the method of Example 4.

The above indicates improved scattering with the PVA / MF interaction product, suggesting better paper formation and / or filler distribution in the paper.

6771 8 25

Example 10 Hand sheets were made in a Noble and Wood sheet mold (8 "x 8"), pressed between rolls and dried with a Noble and Wood dryer, Model E-8. The pulp was unbleached western kraft paper pulp, ground to a CSF of 600. Tensile strength properties were determined as in TAPPI method 494-05-70. The results are shown in Table VIII.

Table VIII

Dry breaking- Dry tensile energy Additive Concentration% length (m) _ absorption (J / nr)

No - 4570 82 MF (HE) 0.7 5830 128 2.0 6070 131

Cationic starch 0.7 5480 123 kelys ("Cato" 9) _._ Λ.

2.0 6420 152

Epoxidized aminopolyamide ("Kymene" 557) 0.7 5820 126 3/1 PVA / MF (HE) 0.7 6770 166 from Example 3 2.0 7740 174 3/1 PVA / MF (HE) 0.7 7300 161 from Example 1 2.0 7430 176 From these results it can be seen that PVA / MF reactants have better dry strength and dry toughness than commercial additives and in fact PVA / MF products are better at 0.7% concentration than control products at 2%: n concentration. This advantage is also maintained in the presence of filler.

Example 11 PVA / MF reaction products are also quite effective wet strength agents for paper. This is shown in Table IX.

26.

6771 8

Table IX

Wet breaking length (a) Wet tensile energy Ί .. ^, absorption ^ (J / m ^) .... No kaolin With kaolin r

Additive. — _— - ---— No kaolin With kaolin

Not at all 260 350 4 5

Cationic starch ^ 400 300 7 .5

Epoxidized aminopolyamide ^ 2300 1500 76 45 MF / HE 17 00 1200 55 36 2/1 PVA / HF (HE) 1300 1200 '76 44 from Example 4 (a' determined with unbleached western kraft paper pulp, ground to a CSF value of 600. Results on hand sheets; additive level 2 % calculated on the dry mass, filler content 10% on the dry mass of kaolin.

(b) "Cato" 9 (c) "Kymene" 557 The PVA / MF reaction product shows better wet strength, wet tensile energy absorption (TEA) than commercial MF resin alone or, of course, cationic starch, which is known to lack any wet strength properties. The epoxidized aminopolyamide appears to be somewhat superior to the PVA / MF product of this invention in wet strength (wet break length). However, epoxidized aminopolyamide is much more expensive and also much inferior to polyvinyl alcohol / melamine-formaldehyde product in terms of waste or waste paper recovery.

Example 12 This example illustrates that the epoxidized aminopolyamide ("Kymene" 557) is much inferior to the polyvinyl alcohol / melamine-formaldehyde reaction product of this invention in terms of waste or waste paper recovery. This is shown in Table X, where the results on paper made from bleached kraft paper pulps on a flat wire machine show a loss of wet strength of the paper when the paper is heated in a very dilute acid solution. Such a loss of strength is, of course, necessary for easy paper recovery. Apparently, paper containing a polyvinyl alcohol / melamine-formaldehyde additive decomposes more easily with dilute acid than melamine-formaldehyde resin alone and quite obviously much more easily than epoxidized aminopolyamide.

27

Table X 6771 8 Wet Break Length ^ Wet Tensile Energy

Additive _ _ absorption.La). (J / nr) 'Ho0 / 25 ° C / 0.02SN HCl / ^ 0/2 5 = 0 / Q.Q25NHCl / 0.5 h. 90 ° C / 0.5 h. Q.5> 90 ° C / 0a5 h._

Not at all 78 78 lf2 112

Cationic starch (b) 197 130 1.6 '1.6 3/1 FVA / MV 1012 213 28.4 2.1 from Example 4 MF (HE) 1497 409 24.4 2.6 ly amide (e) ^ 1500. ^ 1490 ^ 28.0 ^ 27.0 (a) Machine sheets on a flat wire machine, bleached hardwood / softwood-pulp pulp mixture 70/30, ground to a CSF of 500, All additives at a concentration of 2%, calculated on the dry mass, (b) "Cato" 9 (c) "Kymene" 557. The change in wet property values in acid treatment using this additive was evaluated from data contained in an article prepared by ME Carr et al., TAPPI 60,

Well. 10, Oct (1977) pp. 66-69.

Example 13

An aqueous solution containing 2/1 by weight of crude potato starch and MF (HE) in a weight ratio of 3/1 was prepared in an analogous manner to the 3/1 PVA / MF (HE) reaction product. The 3/1/1 starch / PVA / MF (HE) reaction product was also prepared in the same manner. In these cases, the MF (HE) resin acid colloid was prepared as in Example A and the latter was then reacted with potato starch and / or polyvinyl alcohol as in Example 4. The three solutions of starch / melamine-formaldehyde and starch / polyvinyl alcohol / melamine-formaldehyde were ) weeks, while polyvinyl alcohol / melamine-formaldehyde was stable for more than three (3) months. Hand sheets were made using bleached sulfite pulp. A list of the properties of the hand sheets, together with a check sheet that did not contain wet end additives, is given in Table XI. Thus, the superiority of 3/1 polyvinyl alcohol / melamine-formaldehyde over 3/1 starch / melamine-formaldehyde is seen in solution stability and paper properties.

In fact, in many properties, 3/1 polyvinyl alcohol / melamine-formaldehyde at 0.7% concentration is as good or better than 28/1 7 7 7 1 8 than 3/1 starch / melamine-formaldehyde at 2% concentration.

3/1/1 starch / polyvinyl alcohol / melamine formaldehyde is also better than 3/1 starch / melamine formaldehyde.

Table XI

~ Additive 37T “371 37171 PVA / MF starch / MF starch / PVA / MF (a) no -

Barracks antiquities law, 0.7% 2rG% 2.0% 2.0%

Measurement of puncture resistance (Mullen) 19 30 35 25 31

Tear strength measure 88 114 118 69 104 (Elmendorff). 12 23 33 23 38

Tax duration (poxkxttais- _.

direction, (ΜΓΤ) (ΙΠΡ1

Dry breaking length (m) 2950 4200 4900 3760 4570

Dry tensile energy absorption ^ 5 83 80 77 84 (TEA) (J / m2)

Dry start module (PS0) 150 220 290 250 240 Wet break length (m) 230 360 630 270 290 Wet traction energy absorption 5 9 21 9 8 (TEA) (J / m2) Wet start module (KPSI) 8 8 15 9 10

Bleached Northern Sulphite Pulp, CSF 500, Sheets aged-1 tu one (1) month ^ Value in brackets for sheet aged two (2) months.

When the paper contained kaolin at a concentration of 10%, similar advantages of 3/1 PVA / MF over 3/1 starch / MF were found in puncture resistance, flexural strength and dry and wet breaking length, as well as tensile energy absorption. Again, 3/1/1 starch / PVA / MF showed some advantages over 3/1 starch / MF. The results are summarized in Table XII.

6771 8 29

Table XII

Additive T / l 3/1 3/1/1

Hand sheet,, PVA / MF starch / HF starch / PVA / MF

properties ^ a Not at all ^ 0 ^ 7% 2 ^ 0% 2.0% 2.0%

Puncture resistance new 22 28 16 22 dimension (Mullen)

Repij ^ strength strength 1Q0 m m 109 10S

Luxu (Elmendorff)

Bending resistance (transverse direction, MIT) 7 10 26 12 15

Dry breaking length (m) 2600 3370 4090 2690 3440

Dry TEA (J / m2) 26 52 '75 49 57

Dry start module (KPSI) 180 230 250 250 220 Wet break length (m) 160 180 540 160 230 wet TEA (J / m2) 3.5 5 18 5 6 Wet start module (KPSI) 9 9 12 6 11

Bleached northern sulphite pulp, CSF 500. Sheets containing 10% kaolin. Obsolete one (1) month.

Values extrapolated from hand sheets containing 0% and 2% kaolin.

Example 1U

This example illustrates the use of higher aldehydes to modify PVA / MF reaction products. In run (C), a "high power" melamine-formaldehyde acid colloid was prepared as in Example A.

At times (D) and (E), instead of additional formaldehyde, acetaldehyde was added during the "maturation" of the MF resin acid colloid. These were then added to the pulp and the hand sheets were prepared. Table VIII shows the adsorption of additives on the pulp and the properties of the resulting paper sheet. It is clear that when acetaldehyde was added, the results were at least as good when the formaldehyde was added in terms of dry properties.

Table XIII

30 6771 8 Hand Sheet Features (c)

Adsorbent- Mullen-blown- Dry breaking masking- length (m) ·

Additive I get C% _), (a) new ____, - 39 5800 (A) Not at all (B) PVA 4.9 (C) 2/1 PVA / MF 96.8 48 6900 (formaldehyde.) (66% ( (d) (D) 2/1 PVA / MF 94 9 49 7200 (acetaldehyde) (65%) (d) '(!.' Ml PVA / MF - 49 7800 (acetaldehyde) (23%) (d)

Table XIII (continued) 31 6771 8 Hand Sheet Properties (c)

Adsorb- Mullen-blow- Dry break-

Additive ^ td to masking length (m) - to (%) (a) cheese (A) Not at all 100 76 220 (B) PVA - (C) 2/1 PVA / MF 105 97 1800 (formaldehyde) ( 66%) (d) (D) 2/1 PVA / MF 124 105 1380 (acetaldehyde) (66%) (d) (E) 2/1 PVA / MF 142 105 1520 (acetaldehyde) (23%) (d) (a) Determined as described in footnote (b) to Table I (b) with 2% additive based on dry pulp (c) Made from unbleached kraft pulp, CSF .600, no filler or glue included. Measurements using TAPPI procedures as in Table XI.

(d) The percentage indicated is the concentration by weight of aldehyde in relation to the trimethylol melamine used in the manufacture of MF resin acid colloid.

(e) Measured at 0/25 ° C / 0.5 h after exposure.

3 ^ (f) in units of ft-lbx10. TAPPI Method No. 403 was followed.

Example 15 This example illustrates the utility of PVA / MF reaction products to which dialdehyde, glutaraldehyde, was added during the maturation process of MF resin acid colloid. Runs (B), (c) and (D) were performed following the general procedure of Example 14. The results are summarized in Table XIV, which compares the addition of glutaraldehyde to the addition of formaldehyde. The solution stability of the glutaraldehyde-modified product was significantly worse than that of the formaldehyde-modified products. In any case, when the product is used shortly after preparation, the stability of the filler in the pulp is surprisingly high when glutaraldehyde is used. Good paper properties were also obtained, although the content of products added to the pulp 32 6771 8 was lower than in Example 14. Improved solution stability (at least 5 days) was achieved with less glutaraldehyde (13% by weight based on MF resin).

Table XIV

,. Scott

Additive ^ Solution stable- Internal 2 bond of the filler (e) _ stability (%) (c) (d) Ckj / ffl) ___ (A) Not at all - 1.3 42 0.088 (B) 2/1 PVA / MF> 3 mo . 5.2 49 0.103 (formaldehyde) (66%) (b) (C) 2/1 PVA / MF> 3 mo. 7.6 63 0.132 (formaldehyde) (23%) (b) (D) 2/1 PVA / MF ^ 48 h 11.0 75 0.158 (glutaraldehyde) (23%) (b)

Table XIV (cont'd) 33 6771 8

Additive Wet breaking- Wet tensile energy length, absorption (J / m?) (D) (m) (d) _ ______ (A) Not at all 220 4 (B) 2/1 PVA / MF 840 17 (formaldehyde) (66% ) (b) (C) 2/1 PVA / MF 900 18 (formaldehyde) (23%) (b) (D) 2/1 PVA / MF 1000 26 (glutaraldehyde) (23%) (b) (a) 0 , With an additive concentration of 7% by weight. No glue or alum present. The pulp is unbleached kraft pulp as used in Example 10.

(b) Aldehyde concentration as a percentage by weight of trimethylol-melamine (c) Kaolin filler results at low shear rate. Kaolin was added at 20% by weight of the dry mass.

(d) Zero amount of filler. Results for Scott's internal bond in ft · Ib x 1000.

(e) Refers to the stability of the additive solutions compared to a dry matter concentration of 2%.

Claims (21)

34 6771 8 A stable aqueous polyvinyl alcohol / melamine-formaldehyde resin reaction product used to improve the wet strength, dry strength and other properties of products derived from fibrous cellulosic material, e.g. with a dry weight ratio of maldehyde resin to acid colloid of about 1: 1 to 5: 1, and a sufficient amount of water to provide a dry matter content ranging from about 0.7% by weight to a level that does not cause the gel to drain under gravity in 48 hours, but not more than 5% by weight, wherein the logarithmic viscosity number of the polyvinyl alcohol polymer used is about 0.3 to 1.4 dl / g measured in water at 30 ° C at a concentration of 0.5 g / dl, and wherein the polyvinyl alcohol / melamine formaldehyde resin reaction product may further contains up to about 6 parts by weight starch which is unmodified, modified or degraded starch or a starch derivative per part by weight of polyvinyl alcohol. The product according to claim 1, characterized in that the dry matter content of the polyvinyl alcohol / melamine formaldehyde resin acid colloid reaction product is about 0.7 to 3.75% by weight. The product of claim 2, characterized in that the polyvinyl alcohol polymer is at least about 99 mole percent hydrolyzed. The product according to claim 1, characterized in that the logarithmic viscosity number of the polyvinyl alcohol polymer is about 0.5-1.1 dl / g. Product according to Claim 2, characterized in that the polyvinyl alcohol polymer is a copolymer consisting of vinyl alcohol and at most about 10 mol% of a comonomer which is a 2- (olefin) having 2 to 18 carbon atoms, a vinyl ester of saturated carboxylic acids, in the acid part of which is an unsaturated mono- or dicarboxylic acid having up to 18 carbon atoms, 3 to 5 carbon atoms or an ester of said unsaturated mono- or dicarboxylic acids having 1 to 8 carbon atoms in the alcohol moiety, an N-substituted amide of unsaturated monocarboxylic acids, an allyl alcohol, or a saturated having up to 18 carbon atoms or vinyl halide in the acid moiety. Product according to Claim 5, characterized in that the melamine-formaldehyde resin acid colloid is prepared by adding about 8 to 100% by weight, based on the weight of trimethylol melamine, of aldehyde having up to about 10 carbon atoms to water-dissolved trimethylol melamine and aging said solution in the presence of about 0.6 to 0.8 moles of hydrochloric acid per mole of trimethylol melamine. Product according to Claim 6, characterized in that the aldehyde is formaldehyde or a homologue thereof, a substituted aldehyde or a polyaldehyde. Product according to Claim 7, characterized in that the aldehyde is formaldehyde, acetaldehyde or glutaraldehyde. The product according to claim 2, characterized in that it has a dry matter content of about 2-3% by weight. Product according to Claim 9, characterized in that the weight ratio of polyvinyl alcohol to melamine formaldehyde resin acid colloid, based on the weight, is about 2: 1 to 3: 1. The product of claim 1, characterized in that it contains at most about 3 parts by weight of starch per part by weight of polyvinyl alcohol. 12. A process for preparing a stable aqueous polyvinyl alcohol / melamine formaldehyde resin reaction product used to improve the dry strength, dry strength and acid aldehyde formaldehyde formaldehyde formaldehyde polyaldehyde-aldehyde-aldehyde-aldehyde polyol from about 1: 1 to 5: 1, and from a sufficient amount of water to provide a dry matter content ranging from about 0.7% by weight to a level that does not cause gelation in the non-draining state by gravity. subjected to the action for 48 hours, but not more than 5% by weight, wherein the logarithmic viscosity number of the polyvinyl alcohol polymer used is about 0.3 to 1.4 dl / g measured in water at 30 ° C at a concentration of 0.5 g / dl, and wherein the polyvinyl alcohol / melamine formaldehyde resin reaction product may be added contains not more than about 6 parts by weight of starch which is unmodified, modified or decomposed starch or starch derivative, per part by weight of polyvinyl alcohol, characterized in that (a) an acidic colloid of cationic melamine formaldehyde resin is prepared, (b) mixed with m a formaldehyde resin acid colloid with polyvinyl alcohol for a time sufficient to obtain the polyvinyl alcohol / melamine-formaldehyde resin reaction product at a given mixing temperature in the presence of sufficient water to provide a dry matter content in the range of about 0.7% by weight; not more than 6% by weight, the weight ratio of polyvinyl alcohol to melamine formaldehyde resin acid colloid, based on dry weight, being about 1: 1 to 5: 1, optionally up to about 6 parts by weight of starch, unmodified, modified or dispersed starch or starch n, per part by weight of polyvinyl alcohol. Process according to Claim 12, characterized in that the polyvinyl alcohol / melamine formaldehyde resin acid colloid reaction product has a dry matter content of about 0.7 to 3.75% by weight. A method according to claim 13, characterized in that the melamine-formaldehyde resin acid colloid and the polyvinyl alcohol are mixed together at approximately ambient temperature for about 24 hours. The method of claim 13, wherein the melamine formaldehyde resin acid colloid and the polyvinyl alcohol are mixed together at a temperature of about 30 to 90 ° C for about 3 to 15 minutes. 6771 8 Process according to claim 13, characterized in that the polyvinyl alcohol powder or granules are suspended in a melamine-formaldehyde resin acid colloid and the suspension is heated and stirred at a temperature of about 80-95 ° C for about 0.25 to 2 hours or until the polyvinyl alcohol dissolves. A method according to claim 13, characterized in that sufficient water is used to obtain a dry matter content of about 2-3% by weight. Process according to Claim 17, characterized in that the weight ratio of polyvinyl alcohol to melamine formaldehyde resin acid colloid, calculated on the dry weight, is approximately 2: 1 to 3: 1. A method according to claim 13, characterized in that the polyvinyl alcohol is dissolved in water with stirring and heating to obtain a solution of about 10% by weight, the hot polyvinyl alcohol solution is added to about 0.6% by weight of the melamine-formaldehyde resin acid colloid at about ambient temperature and the resulting mixture is stirred gently for about 15 minutes. Process according to Claim 13, characterized in that the starch is present in an amount of about 3 parts by weight per part by weight of polyvinyl alcohol. Process according to any one of claims 13, 17, 18 or 20, characterized in that the polyvinyl alcohol polymer is at least about 99 mol% hydrolysed and has a logarithmic viscosity number of about 0.5 to 1.1 dl / g measured in water. At ° C at a concentration of 0.5 g / dl. 38 6771 8