JPS6116305B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention particularly relates to adhesives used for bonding wood, paper, etc., and its purpose is to provide an adhesive at a low cost that has excellent workability and waterproof adhesion performance. Traditionally, formalin resins such as urea resin, melamine resin, and phenol resin, vinyl acetate resin emulsions, and the like are often used as adhesives for wood and the like. Among these adhesives, formalin-based resin adhesives have excellent water-resistant adhesion performance, but there is a problem that formaldehyde evaporates during or after the adhesion process and gives a stinging tool, and vinyl acetate resin emulsion has water-resistant adhesion properties. Not only is the performance inferior, but there are also problems such as a tendency to cause creep failure after adhesion, and various solutions to these problems have been studied. In recent years, water-based vinyl urethane adhesives in which copolymer resin adhesives of isobutylene and maleic anhydride crosslink polyvinyl alcohol with incyanate compounds have been developed as adhesives that do not use formalin and have excellent water resistance and creep stability. etc. have been developed and have come to be used in some cases. However, these adhesives are more expensive than formalin-based resin adhesives, and because they have good film-forming properties, the adhesive layer dries, resulting in poor adhesion, and water-based vinyl urethane adhesives in particular cannot be used. There are problems such as short time, which is an obstacle in practical use. In addition, when these adhesives are used for heat-pressure bonding, the viscosity of the adhesive decreases significantly as the temperature rises, causing excessive penetration of the adhesive into the adherend material, which can easily cause adhesive failure. There is also the problem of Therefore, in order to prevent excessive penetration of the adhesive, a filler such as wheat flour is added and the thickening properties of the filler are used to prevent penetration, but this method has the disadvantage of reducing water-resistant adhesive performance. This causes other problems such as As a result of repeated research to solve these problems all at once and to develop an inexpensive adhesive, the present inventors used inexpensive starch and added dibasic acid and/or dibasic acid to the starch. An adhesive obtained by adding an incyanate compound having two or more incyanate groups at the end of one molecule to a suspension of half-ester starch obtained by partial esterification with a basic acid anhydride, or The present invention was completed based on the discovery that an adhesive obtained by further blending water-based rubber latex with this adhesive is suitable for this purpose. That is, in the present invention, starch is suspended in water, and in the suspension, per mole of glucose units of starch,
Add 0.1 to 1.0 moles of dibasic acid and/or dibasic acid anhydride, and add an alkaline compound.
To a suspension of semi-esterified starch obtained by performing an esterification reaction at pH 6 to 9, an incyanate compound containing two or more incyanate groups at the end of one molecule is added for crosslinking, or to this, further By adding water-based rubber latex and crosslinking it, an adhesive with excellent workability and water-resistant adhesion performance is produced at a low cost. The first feature of the present invention is that 0.1 to 1.0 moles of dibasic acid and/or dibasic acid anhydride are added to 1 mole of glucose units in starch to half-esterify the starch. It is to form a stable suspension in a state of oxidation. At this time, starch containing 0.1 mol or less of dibasic acid and/or its anhydride per mol of glucose unit of starch will not exhibit a stable suspension state and will precipitate. In addition, if 1.0 mol or more of dibasic acid and/or its anhydride is added, the resulting suspension will cause syneresis phenomenon when left for a long time, which is undesirable because a transparent water layer will be formed on the surface. . Therefore, in the present invention, dibasic acids and/or
Alternatively, it is necessary to adjust the amount of dibasic acid anhydride added to 0.1 to 1.0 mol per mol of glucose unit of starch, and thereby a stable suspension can be obtained. In order to exhibit excellent effects as a drug, 1 glucose unit of starch must be
It is preferable to add 0.2 to 0.5 mol per mol. The second feature of the present invention is that since the semi-esterified starch is suspended in granular form in an ungelatinized state, the starch granules gelatinize and thicken when heated. Therefore, when the water-resistant adhesive of the present invention is bonded by heat and pressure, excessive amount of the adhesive into the adherend is prevented, and stable adhesive performance can be obtained. Therefore, due to this effect, the adhesive of the present invention does not require the addition of an extender such as wheat flour, and is useful for improving work efficiency and preventing deterioration of water-resistant adhesive performance. The third feature of the present invention is that the suspended starch powder absorbs water and exhibits strong water-retaining properties, thereby widening the allowable range of open assembly time. The starch used in the present invention may be any starch or starch derivative that does not dissolve in water at room temperature. For example, starch from corn, potato, sweet potato, wheat, rice, sago, tapioca, sorghum, etc. It can be used regardless of the proportion of amylose and amylopectin. Further, it is also possible to use starches obtained by oxidizing, roasting, or acid-treating these starches, or processed starches obtained by etherifying or esterifying these starches into derivatives. The dibasic acids and/or dibasic acid anhydrides used to produce semi-esterified starch include:
For example, dibasic acids such as oxalic acid, malonic acid, malic acid, succinic acid, glutaric acid, adivic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, phthalic acid, succinic anhydride, adipic anhydride, anhydrous There are maleic acid, itaconic anhydride, phthalic anhydride, etc., and one or more selected from these can be used. The concentration of the semi-esterified starch suspension used in the present invention is within the viscosity range (5 to 5) suitable as an adhesive.
300 voids), any concentration may be used, but a concentration of 5 to 50% is suitable. The incyanate compound used in the present invention may have two or more incyanate groups at the end of one molecule, such as tolylene diincyanate, diphenylmethane diincyanate, naphthalene diincyanate, isophorone diincyanate, etc. Incyanate compounds such as cyanate, hexamethylene diincyanate, xylidene diincyanate, naphthalene diincyanate, etc., and reactants of these incyanate compounds with compounds having hydrogen active toward the incyanate group are suitable. . The appropriate amount of the incyanate compound to be used is 22 to 25 parts by weight per 100 parts by weight of the suspension of semi-esterified starch. , conventionally known fillers such as gypsum, wood flour, walnut starch, etc., wheat flour, defatted soybean flour,
Even if conventionally known bulking agents such as barley flour, rice flour, corn flour, etc., conventionally known thickeners such as polyvinyl alcohol, carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, sodium alginate, guar gum, etc. are blended, the present invention will not be affected. The effect remains the same. A second aspect of the present invention relates to an adhesive obtained by further blending water-based rubber latex with the water-resistant adhesive described above. The present inventors have discovered that more stable water-resistant adhesive performance can be obtained by blending this water-based rubber latex. The aqueous rubber latex used in the present invention includes aqueous rubber latexes such as styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, chloroprene rubber latex, isoprene rubber latex, natural rubber latex, and the like. Or those rubber latexes have carboxyl groups, amide groups,
There are conventionally known aqueous rubber latexes such as modified rubber latexes obtained by incorporating functional groups such as hydroxyl groups and epoxy groups. The appropriate amount of the aqueous rubber latex to be blended is 20 to 200 parts by weight per 100 parts by weight of the semi-esterified starch suspension. The appropriate amount of the aqueous rubber latex to be blended is 20 to 200 parts by weight per 100 parts by weight of the aqueous polymer solution. If the amount of water-based rubber latex added is less than this, the effect of addition will be small, while if it is more than this, the fluidity of the adhesive will decrease and it will become cream-like, which is not preferable. The adhesive of the present invention is suitable as a non-polluting adhesive for bonding wood such as plywood, particle board, laminated wood, furniture, etc., and for bonding paper such as cardboard, paperboard, etc., and is also suitable as a coating agent for paper.
It can also be used as a vehicle for non-polluting paints, and
Cost reduction can be achieved. Next, the present invention will be further explained with reference to Examples. Example 1 100 parts by weight of corn starch was suspended in 400 parts by weight of water, and 22 parts by weight of malic acid was added while stirring.
Approximately 28 parts of 25% caustic soda aqueous solution is added until the pH of the suspension is
After the addition was completed, stirring was continued for an additional hour to complete the reaction. To 20 parts by weight of the suspension thus obtained, 16 parts of calcium carbonate (Whiten P-40, manufactured by Shiraishi Kogyo Co., Ltd.)
Parts by weight and 3 parts by weight of an emulsified diphenylmethane diincyanate compound (manufactured by Hounen Oil Co., Ltd., IB-501) were uniformly mixed to obtain a water-resistant adhesive paste liquid of the present invention. Apply this glue to both sides of a 2.0mm thick lauan veneer.
Apply at a rate of 170 g/m ² (one side), stack 2.0 mm thick lauan veneer on the applied surface so that the fiber directions are perpendicular to each other, and apply temporary pressure at a pressure of 10 kg/cm ² for 30 minutes. After tightening, press the hot press at 120℃ for 8
Heat and pressure bonding was carried out for 2 minutes at a pressure of Kg/cm ² . The adhesive strength of the sample plywood obtained in this way was determined by JAS
It was measured according to the plywood test method. The results are shown in the table below.

[Table] Example 2 100 parts by weight of corn starch was suspended in 400 parts by weight of water, 30 parts by weight of maleic anhydride was added while stirring, and 40 parts by volume of a 25% aqueous solution of caustic soda was added to the suspension.
The mixture was gradually added so that the pH was 6.8, and after the addition was completed, stirring was continued for an additional hour to complete the reaction. Stir the suspension thus obtained for 20 minutes,
Butadiene rubber latex 15 parts by weight, calcium carbonate (manufactured by Shiraishi Kogyo, Whiten P-40) 16
Parts by weight and 3 parts by weight of an emulsified diphenylmethane diincyanate compound (manufactured by Hounen Oil Co., Ltd., IB-501) were uniformly mixed to obtain a water-resistant adhesive paste liquid of the present invention. Apply this glue to both sides of a 2.0mm thick lauan veneer.
It was applied at a rate of 170 g/m ² (one side), and a part of it was layered with 2.0 mm thick lauan veneer on the applied surface so that the fiber directions were perpendicular to each other, and a pressure of 10 kg/cm ² was applied.
After pre-pressing for 30 minutes, heat-pressing was carried out for 2 minutes at a pressure of 8 kg/cm ² using a hot press maintained at 120°C. For the remaining part, the coated surface was exposed to the atmosphere for 60 minutes to allow open assembly time, and then a 2.0 mm thick lauan veneer was layered on the coated surface so that the fiber directions were perpendicular to each other. Temporary compression was performed under the same conditions as described above, and then heat compression bonding was performed. The adhesive strength of the sample plywood obtained in this way was
Measured according to JAB plywood test method. The results are shown in the table below.

[Table] From these results, it can be seen that the water-resistant adhesive of the present invention has excellent water-resistant adhesive performance, is less affected by open assembly time, and is an adhesive with good workability.

Claims (1)

[Claims] 1. A suspension of semi-esterified starch obtained by adding 0.1 to 1.0 mole of dibasic acid and/or dibasic acid anhydride to 1 mole of glucose units of starch and esterifying it, and one molecule of starch. A water-resistant adhesive whose main component is an incyanate compound containing two or more incyanate groups at the end. 2. A suspension of half-ester starch esterified by adding 0.1 to 1.0 mol of dibasic acid and/or dibasic acid anhydride to 1 mol of glucose units of starch;
A water-resistant adhesive whose main components are an incyanate compound containing two or more incyanate groups at the end of one molecule, and water-based rubber latex.