JPS6214575B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a polymer composition comprising raw starch and long-chain alkyl group-modified polyvinyl alcohol and exhibiting unique compatibility behavior. Taking advantage of its water solubility and low cost, starch can be used in conjunction with polyvinyl alcohol to create warp sizing agents,
It can be expected to be used for applications such as paper processing agents and film formation. However, wheat, corn, rice,
"Raw starch" obtained from Umareishiyo, Amashiyo, tapioca, sago palm, etc. has poor compatibility with polyvinyl alcohol, so the film obtained from a mixed aqueous solution of raw starch and polyvinyl alcohol has a sea-island shape. In addition to being low in transparency, repeated heating and cooling of the aqueous solution increases the viscosity each time, resulting in poor stability. Therefore, in order to improve this, it is widely practiced to use various modified starches, such as starch decomposition products such as dextrin, oxidized starch, and acid-treated starch, and starch derivatives such as etherified starch, esterified starch, and crosslinked starch. Since starch decomposition products are depolymerization products of starch molecules, the original properties of starch are impaired, and films and coatings formed from mixed aqueous solutions with polyvinyl alcohol cannot necessarily be said to have satisfactory physical properties. Moreover, starch derivatives do not have particularly good properties considering their cost, and the combination of starch derivatives and polyvinyl alcohol is industrially disadvantageous. However, as a result of intensive research by the present inventors,
It is produced by saponifying raw starch (A) and a copolymer of vinyl ester and an unsaturated monomer having a long chain alkyl group of 4 to 20 carbon atoms, and the long chain alkyl group content is
A composition comprising long-chain alkyl-modified polyvinyl alcohol (B) having water solubility at 0.05 to 10 mol%, wherein the haze of a film formed from the composition is (A)
We have discovered that a polymer composition that exhibits a property of having a haze smaller than that of (A) alone, even when the film has the same weight ratio of (A) and (B), exhibits the excellent effects listed below. The invention was completed. (1) The polymer composition of the present invention has better storage stability in an aqueous solution state than a mixture of raw starch and polyvinyl alcohol. In the system of the present invention, separation of the starch portion is prevented even at low temperatures and low concentrations, and a homogeneous and stable aqueous solution state of both is maintained. (2) The film formed from the aqueous solution of the polymer composition of the present invention is extremely homogeneous and has high transparency.
This situation will be explained in Figure 1. The horizontal axis shows the blending ratio of cornstarch and polyvinyl alcohol or long-chain alkyl group-modified polyvinyl alcohol, and the vertical axis shows the haze of the film, that is, the haze value. The types of polymers used and film production conditions will be detailed later as examples and comparative examples. Curves 2 and 3 in Figure 1 are two examples showing the haze of films obtained by forming films from aqueous solutions of mixtures of corn starch and polyvinyl alcohol in various proportions; It can be seen that the haze of the mixed film is significantly higher than that of the film, and that the haze of the film is highest when the mixed amounts of both are approximately equal in weight. When a mixed film of any ratio of the two is viewed with a magnifying glass or a microscope, it can be seen at a glance that the compatibility of the two is extremely poor. On the other hand, curve 1 in Fig. 1 represents the haze of films obtained by forming films from aqueous solutions of mixtures of corn starch and α-dodecene-modified polyvinyl alcohol in various proportions; It can be seen that the haze is smaller than that of the cornstarch film alone. When a mixed film of the two in any ratio is viewed with a magnifying glass or a microscope, it can be confirmed that the two are extremely uniformly dissolved. (3) The polymer composition of the present invention exhibits almost the same viscosity curve even when its aqueous solution is repeatedly heated and cooled, and is reversible. This situation will be explained using Figures 2 to 4. FIG. 3 is a heating-cooling cyclic viscosity curve of a 5% aqueous solution of corn starch alone. Curve #1 is the viscosity curve when corn starch is gelatinized by heating and then left to cool. Curve #2 is the viscosity curve when it is reheated and then left to cool. Curve #3 is the viscosity curve when it is left to cool after being reheated. This is the viscosity curve of From FIG. 3, it can be seen that corn starch ages as it cools, and that it no longer returns to its original shape even if it is reheated.
This aging phenomenon is said to be mainly due to crystallization of amylose moieties in starch. Figure 4 shows the mixture of a 5% aqueous solution of cornstarch and a 10% aqueous solution of polyvinyl alcohol so that the ratio of cornstarch to polyvinyl alcohol is 2:1 (solid line) or 1:2 (dotted line) by weight. It is a heating-cooling cyclic viscosity curve of an aqueous solution. Curve #1 is the viscosity curve during the first heating-cooling, and curve #2 is the viscosity curve during the second heating-cooling. In this system as well, starch aging phenomenon is observed and the viscosity shows irreversibility. The solid line in Figure 2 indicates the concentration of 5% aqueous solution of corn starch and α-dodecene modified polyvinyl alcohol.
This is a heating-cooling cyclic viscosity curve of a mixed aqueous solution when a 10% aqueous solution is mixed so that the ratio of corn starch to modified polyvinyl alcohol is 2:1 by weight. Curve #1 is the first heating
Cooling curve #2 is the viscosity curve during the second heating-cooling period, and since these two curves almost match and show reversibility, in this system starch aging phenomenon is not caused by its viscosity properties. It can be seen that this is not observed at all. Starch with a reduced ratio of α-olefin modified polyvinyl alcohol: Even when the ratio of α-olefin modified polyvinyl alcohol is 9:1 and 1:2, the viscosity curves are approximately the same as shown by the dashed line and dotted line in Figure 2, respectively. Shows reversibility. Although not shown, heating
Even if the cooling is repeated three or four times, the viscosity curve remains almost unchanged. (4) Furthermore, the film or coating of the polymer composition of the present invention has high mechanical strength, and has the effect of high adhesive strength when bonding paper or plywood using an aqueous solution of the polymer composition. play. Examples of the raw starch (A) in the present invention include wheat starch, corn starch, rice starch, horse starch, amashiyo starch, tapioca starch, sago palm starch, and the like. The aging phenomenon of starch is said to be caused by amylose in starch. Therefore, the present invention is particularly effective for corn starch and wheat starch with a high amylose content, and for starches with a low amylose content. For example, cornstarch starch is less effective than cornstarch. So-called modified starch is not included in the raw starch (A) referred to in the present invention. Long-chain alkyl group-modified polyvinyl alcohol (B) is produced by saponifying a copolymer of vinyl ester and an unsaturated monomer having a long-chain alkyl group with 4 to 20 carbon atoms. A long-chain alkyl group-modified polyvinyl alcohol having a content of 0.05 to 10 mol% and having water solubility. Such modified polyvinyl alcohol can be produced by the following method. (a) A method of copolymerizing a vinyl ester (especially vinyl acetate) and an α-olefin having 4 to 20 carbon atoms, followed by saponification. (b) A method of copolymerizing a vinyl ester (especially vinyl acetate) and an alkyl group having 4 to 20 carbon atoms. A method of copolymerizing a vinyl ester (especially vinyl formate or vinyl acetate) with an alkyl vinyl ether having an alkyl group of 4 to 20 carbon atoms, followed by saponification. Methods Among these methods for obtaining modified polyvinyl alcohol, (a) and (b) are particularly practical. The number of carbon atoms in the long chain alkyl group used is 4 to 20 as described above. If the number of carbon atoms is less than 4, the compatibility with raw starch is poor, while if the number of carbon atoms exceeds 20, the content of the long chain alkyl group is If the content is not reduced, water solubility cannot be obtained, but if the content is reduced enough to obtain water solubility, compatibility with raw starch becomes insufficient. A particularly preferable range is 8 to 8 carbon atoms.
It was when I was 20. The proportion of such long-chain alkyl groups in the polymer is selected from the range of 0.05 to 10 mol%; if the proportion is less than 0.05 mol%, the compatibility with raw starch is insufficient, while if it exceeds 10 mol%, carbon Even if you choose a small number, it will be insoluble in water. A particularly preferred range is 0.05 to 2 mol%. The saponification degree of modified polyvinyl alcohol is 50~
100 mol%, especially 80 to 100 mol%, is suitable; if the degree of saponification is too low, water solubility will be impaired and compatibility with raw starch will be poor. Depending on the composition, the modified polyvinyl alcohol having the above composition may not exhibit water solubility. For example, if the alkyl group has a large number of carbon atoms and is highly modified, or if the degree of saponification is low, it will be difficult to dissolve in water. Therefore, cases where it is water-insoluble are excluded from the scope of the present invention. However, for example, when copolymerizing a monomer with a long-chain alkyl group with a vinyl ester, unsaturated carboxylic acid compounds (acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, etc., or salts thereof, anhydrous When a small amount of an unsaturated sulfonic acid compound (ethylene sulfonic acid, allyl sulfonic acid, meta-allylsulfonic acid, etc., or a salt thereof) is present, the resulting copolymer is saponified. The modified polyvinyl alcohol becomes water-soluble. Further, long-chain alkyl group-modified polyvinyl alcohol that is insoluble in pure water may become water-soluble if an anionic surfactant coexists with it. Therefore, if it is made water-soluble by some means, it falls within the scope of the present invention. As shown in Figure 1, the blending ratio (by weight) of raw starch (A) and modified polyvinyl alcohol (B) changes from when a small amount of (B) is blended to (A) to (B) to (A). A clear effect can be achieved at any ratio even when a small amount of (A):(B)=1:99~
You can choose from a wide range such as 99:1, especially (A):(B) = 10:90 to 90:10. Further, if we break down the cases from the standpoint of usage, we will get the following. If the purpose is simply to prevent the aging of raw starch (A), it is sufficient to blend 1% by weight or more of modified polyvinyl alcohol (B) with respect to raw starch (A). A preferred range is (A):(B)=95:5 to 70:30, especially 95:5 to 80:20 by weight. If the proportion of (B) is too low, the effect will be poor, while if the proportion of (B) is too high, the properties of raw starch (A) will change accordingly and the cost will increase. Such a formulation is useful, for example, for starch paste applications, including adhesive applications for plywood, cardboard, general use, etc., ie, for cooking starch applications. When using modified polyvinyl alcohol (B) in place of conventional polyvinyl alcohol in the application of a combination formulation of raw starch (A) and polyvinyl alcohol, by weight (A): (B) = 95: 5 to 5: 95 especially (A):(B)~90:10~10:90 is often adopted. Such a formulation is useful, for example, as a fiber sizing agent, especially a warp sizing agent, a paper processing agent, an adhesive, a film forming agent, and the like. In particular, this formulation is most suitable for use as a warp sizing agent. In cases where raw starch (A) is used to modify modified polyvinyl alcohol (B), the ratio of both by weight is (A):(B)=1:99 to 40:60, especially (A):(B). )
= 5:95 to 30:70 in many cases. Such formulations are useful for applications such as paper diapers, leak-proof films for absorbent cotton, transfer printing films, water-soluble packaging films, and agricultural water-soluble films. The combination of raw starch (A) suppresses film elongation and strengthens the waist.
There are advantages such as ease of film formation. Raw starch (A) and modified starch (B) can be mixed by mixing them in powder form and then adding water or pouring them into water to gelatinize them, or by gelatinizing (A) and (B) separately. Any method can be used, such as a method in which the mixture is mixed after oxidation. Various additives such as plasticizers, colorants, fillers, salts, boric acid or borax, and surfactants may be added to the mixture, and other water-soluble polymers may also be added. Now, even if the above-mentioned raw starch (A) and long-chain alkyl group-modified polyvinyl alcohol (B) are used together, the type of (A), the type of long-chain alkyl group of (B), the amount of modification, and the amount of modification in the copolymer. Distribution, degree of saponification of (B), degree of polymerization, (A) and (B)
The desired effect may not be achieved depending on the combination of conditions such as the blending ratio. To describe two or three trends, raw starch (A) exhibits the desired effect more clearly as it has a higher amylose content, as mentioned above, due to its type. The larger the number of carbon atoms in the long-chain alkyl group (B), the more likely it is to exhibit the desired effect, while the relatively smaller number of carbon atoms will result in a slightly poorer effect. Therefore, when relatively unfavorable conditions are adopted among these conditions, for example, when using horsereishiyo starch with relatively low amylose content as (A), depending on the combination with other conditions, the desired result may not be achieved. It may not be effective. Therefore, in the present invention, the haze of the film formed from the aqueous solution of the composition is not limited to the composition simply consisting of (A) and (B). Even if the film has a certain ratio, there is an additional requirement that it exhibits a characteristic that is smaller than the haze of (A) alone. The specific conditions for measuring haze are as shown in Example 1. Therefore, a film that violates this requirement, that is, a film formed from an aqueous solution of a 1:1 mixture of (A) and (B) by weight, whose haze is higher than that of the film of (A) alone, is not covered by the present invention. excluded from the scope of This is because (A) and (B) are essentially incompatible with such a material, and even if it is possible to form it into a film or film, it will have a sea-island structure. Next, the polymer composition of the present invention will be further explained by giving examples. In the following, "parts" and "%" are expressed on a weight basis, unless otherwise specified and excluding percentages of haze. Example 1 Add cornstarch to 50℃ hot water and raise the temperature.
The mixture was heated and stirred at 95 to 100°C for 4 hours to gelatinize and prepare a 7% aqueous solution. Alternatively, α-dodecene-modified polyvinyl alcohol obtained by saponifying 99 mol% of the vinyl acetate component of an α-dodecene-vinyl acetate copolymer with an α-dodecene content of 0.2 mol% is poured into water and dissolved by heating. A 7% aqueous solution was prepared. The above two types of aqueous solutions and these when heated 9:1,
Film formation was performed using five types of aqueous solutions mixed at ratios of 7:3, 5:5, 3:7, and 1:9. Film production is
The above aqueous solution was poured onto a glass plate placed on a hot plate and a polyethylene terephthalate sheet was pasted thereon, and the water was evaporated while maintaining the temperature at 70 to 80°C. The film thickness was set to 45±5μ. The haze of the film thus obtained was measured with standard C light using a reflection transmittance meter manufactured by Murakami Color Research Institute. The results are shown in curve 1 in Figure 1, and the haze of the 1:1 mixture film of corn starch and α-dodecene-modified polyvinyl alcohol is smaller than the haze of 20.9% for the corn starch-only film, which is a requirement of the present invention. It can be seen that the curve 1 satisfies the following, and no local maximum value is observed in curve 1, and the absolute value of haze is also low. When this film was observed using a magnifying glass and a polarizing microscope, it was found that the film was extremely homogeneous and had excellent compatibility. Control Examples 1 to 2 Polyvinyl alcohol with a degree of polymerization of 1800 and a degree of saponification of 99 mol% (control example 1), a degree of polymerization of 1700 and a degree of saponification of 89 in place of α-dodecene-modified polyvinyl alcohol
The haze of the film of the mixture with corn starch was measured in the same manner as in Example 1 except that mol % of polyvinyl alcohol (Control Example 2) was used. The results are shown in curve 2 (control example 1) and curve 3 in Figure 1.
(Comparative Example 2), both have maximum values at a 1:1 mixing ratio of cornstarch and polyvinyl alcohol, and the absolute value is 50.3% (Comparative Example 1), compared to the haze of 20.9% for the cornstarch-only film. ), which was significantly high at 58.6% (Control Example 2). Furthermore, it was confirmed that the films of Control Example 1 and Control Example 2 had poor compatibility when observed using a magnifying glass, and when observed using a polarizing microscope. Examples 2 to 5 Cornstarch was completely gelatinized at 95°C for 2 hours to prepare a 5% aqueous solution. A 10% aqueous solution of the α-dodecene modified polyvinyl alcohol of Example 1 was also prepared. The above two types of aqueous solutions are mixed with corn starch and α-dodecene modified polyvinyl alcohol at a blending ratio of 2:1.
(Example 2), 9:1 (Example 3), and 1:2 (Example 4) at a temperature of 85 to 90°C, and the viscosity was measured using a B-type viscometer while cooling. This paste solution that had been allowed to cool was reheated at 85 to 90° C. for 20 minutes, and its viscosity was measured while allowing it to cool again. The results are shown in Figure 2. Solid line #1 in Figure 2 is example 2
The solid line #2 is the first heating-cooling viscosity curve of Example 3, the solid line #2 is the second heating-cooling viscosity curve, the dashed-dotted line #1 is the first heating-cooling viscosity curve of Example 3, and the dashed-dotted line #2
is the second heating-cooling viscosity curve, dotted line #1 is the first heating-cooling viscosity curve of Example 4, and dotted line #2 is the second heating-cooling viscosity curve. The same experiment as above was conducted for the case where the blending ratio of corn starch and α-dodecene-modified polyvinyl alcohol was 19:1 (Example 5), but the viscosity curve almost matched the dashed-dotted lines #1 and #2 of Example 3. Therefore, illustration is omitted. It can also be seen from FIG. 2 that in the polymer composition of the present invention, the viscosity curve of cornstarch does not change even when repeatedly heated and cooled, and the viscosity does not change due to aging, which is generally seen in raw starch. Control Example 3 The heating-cooling cyclic viscosity curve of the 5% cornstarch aqueous solution used in Example 2 is shown in FIG. In Figure 3, #1 shows the viscosity curve when completely gelatinized at 95℃ for 2 hours and left to cool, and #2 shows the viscosity curve when this was reheated at 85-90℃ for 20 minutes and then left to cool. Viscosity curve #3 is the viscosity curve when this was heated again and then allowed to cool. From FIG. 3, it can be seen that corn starch ages as it cools. Control Examples 4 to 5 Experiments were conducted in the same manner as in Examples 2 and 4, except that polyvinyl alcohol having a degree of polymerization of 1700 and a degree of saponification of 89 mol % was used in place of α-dodecene-modified polyvinyl alcohol. The blending ratio of corn starch and polyvinyl alcohol was 2:1 in Control Example 4 and 1:2 in Control Example 5. The results are shown in Figure 4. The solid line in FIG. 4 is Control Example 4, and the dotted line is Control Example 5. #1 is the first heating-cooling viscosity curve, and #2 is the second heating-cooling viscosity curve. It can also be seen from FIG. 4 that in the cornstarch/polyvinyl alcohol combination system, the aging phenomenon of cornstarch appears in the viscosity curve of this combination system in a manner commensurate with the amount of cornstarch. Example 6 95-100 after adding cornstarch to 50℃ hot water
The mixture was heated to ℃ and stirred for 4 hours to prepare a 5% aqueous solution. Dilute this aqueous solution with hot water to 3% at a temperature of 80℃.
I made an aqueous solution. Further, the α-dodecene-modified polyvinyl alcohol of Example 1 was added to water and heated to prepare a 3% aqueous solution at a temperature of 80°C. Mix a cornstarch aqueous solution and an α-dodecene modified polyvinyl alcohol aqueous solution at a temperature of 80°C in the ratio shown in the table below, and place the mixture in a test tube with an inner diameter of 15 mm.
The solution was injected to a height of 1.0 mm, left at 25°C, and its stability was observed over time. The conditions and results are shown in Table 1. From Table 1, it can be seen that the stability of the aqueous solution of the polymer composition of the present invention is extremely good, and the compatibility between corn starch and α-dodecene-modified polyvinyl alcohol is good. Control Examples 6 to 7 Instead of α-dodecene-modified polyvinyl alcohol, polyvinyl alcohol with a degree of polymerization of 1700 and a degree of saponification of 89 mol% (Control Example 6), a degree of polymerization of 2600 and a degree of saponification
The experiment was conducted in the same manner as in Example 6, except that 99 mol% polyvinyl alcohol (Control Example 7) was used. The conditions and results are shown in Table 1. It can be seen that the stability of the corn starch/polyvinyl alcohol mixed system is extremely poor, and the compatibility between the two is poor. Control Example 8 An experiment was conducted in the same manner as in Example 6 using the 3% aqueous cornstarch solution prepared in Example 6. The results are also shown in Table 1.

【table】

[Table] Examples 7 to 15, Control Examples 9 to 10 Raw starch (A) A-1 Corn starch A-2 Wheat starch A-3 Umareishiyo starch A-4 Tapioca starch Long-chain alkyl group-modified polyvinyl alcohol (B) B- 1 α- with α-octadecene content of 0.14 mol%
α-octadecene modified polyvinyl alcohol B-2 obtained by saponifying 98 mol% of the vinyl acetate component of an octadecene-vinyl acetate copolymer Acetic acid of an α-decene-vinyl acetate copolymer with an α-decene content of 0.4 mol% α-decene modified polyvinyl alcohol B-3 obtained by saponifying 90 mol% of the vinyl component α-hexadecene content of 0.4 mol%
α-hexadecene-modified polyvinyl alcohol obtained by saponifying 99 mol% of the vinyl acetate component of hexadecene-vinyl acetate copolymer and B-2
1:1 mixture by weight of α-decene modified polyvinyl alcohol B-4 Dodecyl vinyl ether content 0.3 mol%
Dodecyl vinyl ether-modified polyvinyl alcohol B-5 obtained by saponifying 99 mol% of the vinyl acetate component of the dodecyl vinyl ether-vinyl acetate copolymer Octyl vinyl ether content 0.6 mol%
Octyl vinyl ether-modified polyvinyl alcohol B-6 obtained by saponifying 98 mol% of the vinyl acetate component of the octyl vinyl ether-vinyl acetate copolymer Versatric acid (saturated branched fatty acid with 5 to 11 carbon atoms) Vinyl content 0.9 mol% Vinyl versatility modified polyvinyl alcohol obtained by saponifying 98 mol% of the vinyl acetate component of the vinyl versatility-vinyl acetate copolymer of Measurement, observation using a polarizing microscope, measurement of the viscosity of the aqueous solution, and observation of the storage stability of the aqueous solution were performed. The results are shown in Table 2.

【table】

【table】 [Brief explanation of the drawing]

Figure 1 is a relationship diagram showing the haze of the film created in Example 1, Figure 2 is a relationship diagram showing the viscosity of the aqueous solutions created in Examples 2 to 4, and Figure 3 is a relationship diagram showing the viscosity of the aqueous solutions created in Control Example 3. FIG. 4 is a relational diagram showing the viscosity of the aqueous solutions prepared in Comparative Examples 4 and 5.

Claims (1)

[Scope of Claims] 1 Produced by saponifying a copolymer of raw starch (A) and an unsaturated monomer having a long-chain alkyl group with 4 to 20 carbon atoms and a vinyl ester; A composition comprising water-soluble, long-chain alkyl group-modified polyvinyl alcohol (B) with a content of 0.05 to 10 mol%, wherein the haze of a film formed from an aqueous solution of the composition is the same as that of (A) and (B). (A) A polymer composition with excellent compatibility that exhibits a property that the haze is smaller than that of (A) alone even when the film is in an equal weight ratio with (A). 2. The composition according to claim 1, wherein the mixing ratio of (A) and (B) is 99:1 to 1:99 by weight. 3. The composition according to claim 1, wherein (A) is corn starch or wheat starch. 4. The composition according to claim 1, wherein the unsaturated monomer having a long-chain alkyl group is an α-olefin. 5. The composition according to claim 1, wherein the unsaturated monomer having a long-chain alkyl group is an alkyl vinyl ether.