JPS6342664B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a composition having crosslinking properties. More specifically, an ethylene-vinyl acetate copolymer aqueous dispersion (A) obtained by an emulsion copolymerization reaction using a water-soluble polyvinyl alcohol polymer as a protective colloid and two or more isocyanate groups in one molecule. An aqueous dispersion of a blocked isocyanate compound or a polyisocyanate compound obtained by blocking a polyisocyanate compound having an aqueous solution (B) of a blocked isocyanate compound blocked with an acidic sulfite, and the molar ratio of the isocyanate groups in (B) to the hydroxyl groups of the polyvinyl alcohol in the (A) is equal to or less than the hydroxyl groups of the polyvinyl alcohol. /isocyanate group=1/0.05 to 1/1 (molar ratio). Conventionally, urea resins, melamine-urea cocondensation resins, phenolic resins, etc. have been widely used in adhesives, textile processing agents, and pulp board impregnation processing agents because they are inexpensive, have good adhesive properties, and have good water resistance. However, the formalin generated during the crosslinking reaction causes hygiene problems, and there is a need to switch to other crosslinking agent systems. As other crosslinking agent systems, systems of glycidyl groups and carboxyl groups and systems of isocyanates and functional groups having active hydrogen such as hydroxyl groups and amide groups are known. However, the glycidyl group/carboxyl group system is not only expensive but also has an excessively high reaction temperature, which causes deterioration of the base material, making it unsuitable. In addition, the system of isocyanate and functional groups having active hydrogen such as hydroxyl group and amide group is
Although it is known from Japanese Patent No. 37663, it is used only in non-aqueous systems, and when used in aqueous systems, the pot life is short and there are many problems. In addition, a system of an aqueous dispersion containing polyvinyl alcohol (hereinafter abbreviated as PVA) and isocyanate was also published in Japanese Patent Publication No. 50-36264.
Although it is known from Japanese Patent Publication No. 51-30577, these cases also have problems in terms of pot life. Japanese Patent Laid-Open No. 2002-193031 showed a method of using blocked isocyanates as a way to extend the pot life.
It is disclosed in Japanese Patent No. 53-33251. However, in this method, a hydroxyl group or an amide group is introduced into an ethylene-vinyl acetate copolymer by a copolymerization method, and a blocked isocyanate is added to this, but vinyl having these functional groups described in the specification is It is difficult to copolymerize monomers with ethylene and vinyl acetate because they have different copolymerization reactivity ratios, and it is difficult to efficiently introduce these functional groups, but it is difficult to obtain a large crosslinking effect. However, the present inventors pursued an efficient crosslinking reaction between an aqueous dispersion of ethylene-vinyl acetate copolymer, which is flexible and has excellent adhesive properties, and a blocked isocyanate compound, and as a result of intensive research, they succeeded in protecting PVA. An aqueous dispersion of ethylene-vinyl acetate copolymer (A) obtained by an emulsion copolymerization reaction to form a colloid and a polyisocyanate compound having two or more isocyanate groups in one molecule are combined with alcohols, phenols, oxime an aqueous dispersion of a blocked isocyanate compound blocked with a compound selected from the group consisting of mercaptans, amides, imides, and lactams, or a blocked isocyanate compound obtained by blocking a polyisocyanate compound with an acidic sulfite. an aqueous solution (B), and the molar ratio of the isocyanate groups in the (B) to the hydroxyl groups in the polyvinyl alcohol in the (A) is such that the hydroxyl groups in the polyvinyl alcohol/isocyanate groups = 1/0.05 to 1/1 (mol). (ratio) The composition exhibits excellent crosslinking reactivity, that is, excellent water resistance and adhesive properties, and is water-based and has a long pot life, and can be used as adhesives and textiles without causing environmental hygiene problems such as formalin or organic solvents. The present inventors have discovered that it exhibits excellent performance as a processing agent and pulp board processing agent, and have completed the present invention. The ethylene-vinyl acetate copolymer aqueous dispersion (A) used in the present invention uses PVA as a protective colloid, and the ethylene content of the copolymer is 5 to 40.
%, vinyl acetate content is 95 to 60% by weight, preferably ethylene content is 8 to 30% by weight, and vinyl acetate content is emulsion copolymerized under pressure with ethylene to 92 to 70% by weight. used. When the ethylene content is less than 5% by weight, the resin becomes too hard and loses its flexibility. On the other hand, if it exceeds 40% by weight, not only is it not easy to manufacture, but the resin is too soft, resulting in low strength and poor adhesion. PVA as a protective colloid used in the production of the above-mentioned ethylene-vinyl acetate copolymer aqueous dispersion has a degree of polymerization of 300 to 2500 and a degree of saponification of 70 to 70.
In addition to using 100 mol% partially or completely saponified products, unsaturated carboxylic acids such as acrylonitrile, acrylamide, crotonic acid, acrylic acid, methacrylic acid, maleic acid, itaconic acid, and their alkyl esters are converted into acetic acid during the polymerization process. Water-soluble so-called modified PVA or PVA derivatives, such as those copolymerized with vinyl and then saponified, and those produced by producing PVA and then reacting with sulfuric acid, phosphoric acid, formalin, urea, maleic anhydride, etc., can also be used. The amount used is 1 to 1 per ethylene-vinyl acetate copolymer resin.
15% by weight, preferably 2-8% by weight. Further, if necessary, conventionally known anionic activators, nonionic activators, and cationic activators can be used in combination. however
PVA needs to be present in the polymerization reaction system during polymerization, and the aqueous dispersion obtained by polymerizing only in the presence of the above-mentioned activator and adding PVA after polymerization has a small crosslinking effect with isocyanate. The aqueous ethylene-vinyl acetate copolymer dispersion used in the present invention is of the type described above.
Obtained by using PVA under the above conditions. The aqueous dispersion or solution (B) of the blocked isocyanate compound used in the present invention is a polyisocyanate compound having two or more isocyanate groups in one molecule, including alcohols, phenols, oximes, mercaptans, and amides. The polyisocyanate compound is blocked with a compound selected from , imides, and lactams and made into an aqueous dispersion by a conventional method, or a polyisocyanate compound is blocked with an acidic sulfite and made into an aqueous solution. Polyisocyanate compounds include tolylene diisocyanate (TDI), xylidene diisocyanate (XDI), naphthalene diisocyanate (NPDI), hexamethylene diisocyanate (HDI), methylene bis(4-phenyl isocyanate) (MDI), isophorone diisocyanate (IPDI), Mention may be made of trimethylolpropane-TDI adducts and prepolymer polyvalent isocyanates derived therefrom. One of the features of the present invention is the use of blocked isocyanates in the form of aqueous solutions or aqueous dispersions dispersed in fine particle size. The crosslinking reaction system of the present invention is a reaction system between PVA existing on the surface of the ethylene-vinyl acetate copolymer dispersed particles and isocyanate, and both are in the form of an aqueous dispersion in which the particles are dispersed in minute sizes. This is why micro-mixing is facilitated and crosslinking efficiency is improved. Forms other than aqueous dispersions cause the following disadvantages. For example, in the form of a solution of blocked isocyanate in an organic solvent, it is possible to mix it relatively microscopically by mechanical stirring with a large shearing force, but this is not practical since foaming occurs. In addition, in powder form, it is difficult to mix uniformly and microscopically, resulting in a significant drop in crosslinking efficiency. As described above, in the present invention, 2
An aqueous dispersion of a blocked isocyanate compound obtained by blocking a polyisocyanate compound having 1 or more isocyanate groups with a compound selected from alcohols, phenols, oximes, mercaptans, amides, imides, and lactams. Alternatively, it is important to use an aqueous solution of a blocked isocyanate compound, which is obtained by blocking a polyisocyanate compound with an acidic sulfite salt.Therefore, even when a small amount of the blocked isocyanate compound is added, a remarkable crosslinking effect is exhibited. Ethylene-vinyl acetate copolymer aqueous dispersion (A) obtained by emulsion copolymerization reaction using a water-soluble polyvinyl alcohol polymer as a protective colloid.
and a polyisocyanate compound having two or more isocyanate groups in one molecule, an alcohol,
An aqueous dispersion of a blocked isocyanate compound blocked with a compound selected from phenols, oximes, mercaptans, amides, imides, and lactams, or a block made of a polyisocyanate compound blocked with an acidic sulfite. The ratio of the isocyanate compound to the aqueous solution (B) is 1 hydroxyl group of PVA present in the ethylene-vinyl acetate copolymer aqueous dispersion (A).
The isocyanate group present in (B) is blended in an amount of 0.05 to 1 mole per mole. If it is less than 0.05 mol, the crosslinking effect is small, and if it is more than 1 mol, the crosslinking effect hardly changes and is economically disadvantageous. Furthermore, if necessary, organic tin compounds such as stannic acid and dibutyltin dilaurate, and tertiary amines such as triethylamine and triethylenediamine, which are dissociation catalysts for the blocked isocyanate compound, can also be added to the composition of the present invention. Furthermore, additives such as thickeners, plasticizers, antifoaming agents, etc., which are usually added to aqueous resin dispersions, can also be added to the composition of the present invention, if necessary. Specific applications of the crosslinkable composition of the present invention include adhesives between base fabric and leather in the production of vinyl chloride leather, adhesives between vinyl chloride sheets and plywood in the production of vinyl chloride overlays, and urethane foam in urethane foam laminates. Adhesives for textiles, adhesives for textiles in bonded fabrics, binders for nonwoven fabrics, texture improving agents for textiles, impregnating agents for pulp boards, etc. for flexibility, adhesive strength, solvent resistance, Used for applications that require water resistance. As a method of using the crosslinkable composition of the present invention,
A polyisocyanate compound having two or more isocyanate groups in one molecule is added to an aqueous dispersion of ethylene-vinyl acetate copolymer (A) containing PVA as a protective colloid, including alcohols, phenols, oximes, mercaptans, and amides. An aqueous dispersion of a blocked isocyanate compound obtained by blocking with one kind of compound selected from , imides, and lactams or an aqueous solution (B) of a blocked isocyanate compound obtained by blocking a polyisocyanate compound with an acidic sulfite. The molar ratio of the isocyanate groups in (B) to the hydroxyl groups in polyvinyl alcohol in (A) is hydroxyl groups in polyvinyl alcohol/isocyanate groups = 1/0.05 to 1/1 (molar ratio). A common method is to prepare a product, adjust it to an appropriate viscosity, impregnate or coat it on a substrate, and then heat treat it at 120°C to 190°C. In this case, if the heat treatment conditions are lower than 120°C, the blocked isocyanate will not dissociate and therefore no crosslinking reaction will occur. Furthermore, high temperatures of 190° C. or higher are not preferred because the base material undergoes significant thermal deterioration. Next, the present invention will be specifically explained with reference to Examples. Hereinafter, unless otherwise specified, "parts" and "%" are expressed on a weight basis. Experimental Example 1 Preparation of an aqueous dispersion of ethylene-vinyl acetate copolymer () containing PVA as a protective colloid: A degree of polymerization of 1700 and a degree of saponification was placed in an autoclave equipped with a stirring device and a jacket capable of controlling temperature.
Dissolve 6 parts of 88 mol% PVA in 70 parts of water, then
After adding and mixing 0.5 part of dibasic sodium phosphate and 10 parts of vinyl acetate as a pH adjuster, ethylene was added to the pressure of 40%.
Press fit up to Kg/cm ² . At an internal temperature of 65° C., 2% potassium persulfate and 30 parts of an aqueous solution are added to initiate polymerization, and 67 parts of vinyl acetate are continuously added over a further 5 hours. After the addition was completed, the reaction was continued for an additional hour. The resulting aqueous dispersion had a solid content of 51.5%, a viscosity of 2200CP,
The ethylene content was 24.3% at pH 4.5. Experimental Example 2 Preparation of an aqueous dispersion of ethylene-vinyl acetate copolymer () in which PVA is not used as a protective colloid during polymerization: In the same autoclave as in Experimental Example 1, 70 parts of 4.5 parts of a nonionic activator (Noniball 400, manufactured by Sanyo Chemical) were added. of water, then added 0.5 parts of dibasic sodium phosphate and 10 parts of vinyl acetate, and then ethylene was dissolved at a pressure of 40 kg/
30 parts of a ² % potassium persulfate aqueous solution was added at an internal temperature of 65° C. to initiate polymerization. During the polymerization, 67 parts of vinyl acetate was continuously added over 5 hours, and after the addition was completed, the reaction was continued for an additional hour. After cooling to a temperature of 30℃, the degree of polymerization is 500, and the degree of saponification is 88 mol% of PVA.
% aqueous solution was added. The resulting aqueous dispersion had a solid content of 48.8%, a viscosity of 980CP, and an ethylene content of 22.5.
It was %. Experimental Example 3 Preparation of an aqueous dispersion of ethylene-vinyl acetate copolymer () containing PVA as a protective colloid: 1 mol% itaconic acid was copolymerized in the same autoclave as in Experimental Example 1, with a degree of polymerization of 500 and a degree of saponification of 85 mol. % modified PVA and 2 parts of a nonionic activator (Noniball 400, manufactured by Sanyo Chemical) are dissolved in 70 parts of water. Next, add 80 parts of vinyl acetate and a second part of PH adjuster.
Add 0.2 parts of sodium phosphate and mix with ethylene.
Press fit up to 45Kg/cm ² . Add 3 parts of 1% hydrogen peroxide solution and 3 parts of 4% tartaric acid solution at an internal temperature of 60°C to start polymerization. Hydrogen peroxide solution and tartaric acid solution are used during polymerization.
12 parts of each were added continuously over time.
The resulting aqueous dispersion had a solids concentration of 50.8% and a viscosity of
250CP, PH5.1, and ethylene content was 20.5%. Example 1 Blocking particles with a particle size of about 0.5μ are dispersed in 100 parts of an aqueous dispersion of ethylene-vinyl acetate copolymer obtained by emulsion copolymerization using PVA as a protective colloid in Experimental Example 1. 5 parts of an aqueous dispersion of an isocyanate compound (an aqueous dispersion of a blocked isocyanate compound in which TDI is blocked with an oxime derivative, solids content 30%, effective NCO content 3.6%) are added. [PVA hydroxyl group/isocyanate group = 13.9 (mole ratio)] The above composition remained stable with no thickening phenomenon observed even after being left at room temperature for 10 days. Add water to the above composition and make 25
A pulp board (basis weight: 600 g/cm ² ) is immersed in the solution adjusted to a solid content of 30%, and squeezed using a roller type squeezer so that the pulp board is impregnated with 30% solid content. Next, after preliminary drying at 40°C for 2 minutes using an infrared lamp, the board was further dried at 140°C for 30 minutes in a hot air dryer to obtain a pulp board with a good texture. The tensile strengths of this resin-impregnated pulp board in the normal state and in the wet state after immersion in water (immersed in water at 20°C for 1 hour) are 32.0 Kg/15 mm and 16.5 Kg/15 mm, respectively, and before resin impregnation and in the aqueous dispersion ( )Water resistance is greatly improved compared to single-system impregnated pulp board. (Table 1)

[Table] Example 2 100 parts of the aqueous dispersion () obtained in Experimental Example 1 was mixed with a blocked isocyanate aqueous solution (an aqueous solution of blocked isocyanate in which HDI was blocked with acidic sodium sulfite, solid content concentration 55%, NCO
Add 3 parts of 12.3%). PVA hydroxyl group/isocyanate group = 6.8 (molar ratio) Water was added to the above composition to adjust the solid content concentration to 5%, and a polyester web (basis weight 15 g/m ² ) was added to the solution.
The fibers were layered in six layers and dipped, squeezed with a mangle so that the resin content was 20% based on the weight of the fibers, dried at 60°C for 60 minutes, and then heat-treated at 150°C for 3 minutes. The obtained nonwoven fabric had a good texture, a tensile strength of 2.1 kg/25 mm under normal conditions, and a water resistance strength (after immersion at 20° C. for 30 minutes) of 1.2 kg/25 mm, indicating excellent water resistance. Example 3 To 100 parts of the aqueous dispersion obtained in Experimental Example 1, 7 parts of the blocked isocyanate aqueous dispersion used in Example 1 was added to obtain a composition. PVA hydroxyl group/isocyanate group = 9.9 (mole ratio) 140g/
Apply a coating amount of 2 m ² and attach a 300μ thick soft vinyl sheet. After air drying, it was hot pressed at 150°C for 1 minute, and the 180° peel strength was measured. 6.0 under normal conditions
Kg/25mm (100% wood breakage), 5.5Kg/25mm (100% wood breakage) even in a wet state after 24 hours of immersion in water, which shows almost no decrease. Comparative Example 1 A composition was prepared in the same manner as in Example 3, except that the aqueous dispersion ( ) obtained in Experimental Example 1 was replaced with the aqueous dispersion ( ) obtained in Experimental Example 2. Hydroxyl group/isocyanate group of PVA added after polymerization = 8.9 (mole ratio) This composition was used to bond plywood/soft vinyl chloride sheet. Normal adhesive strength is 3.5Kg/25mm
(shallow wood damage), and the water resistance adhesive strength is 1.5Kg/25mm, and the water resistance strength is 3.0Kg/25mm and 0.9Kg/25mm respectively in the normal state and water resistance strength in the aqueous dispersion () alone system without adding blocked isocyanate compound. ), no significant improvement effect was observed. Example 4 An aqueous dispersion of a blocked isocyanate compound (blocked isocyanate compound obtained by blocking TDI with ethanol) dispersed in 100 parts of the aqueous dispersion obtained in Example 3 with a particle size of about 0.5μ Aqueous dispersion, solids content 25%, effective NCO content 7.9
%) is added. PVA hydroxyl group/isocyanate group=2.2 (mole ratio) The above composition remained stable with no thickening phenomenon observed even after being left at room temperature for 10 days. A polyester web (basis weight 15 g/m ² ) was added to the solution prepared by adding water to the above composition and adjusting the solid content concentration to 5%.
The fibers were soaked in six layers, squeezed with a mangle so that 20% of the fiber weight was impregnated with resin, dried at 60°C for 60 minutes, and then heat-treated at 150°C for 3 minutes. The texture of the obtained nonwoven fabric is good, the tensile strength is 1.9 kg/25 mm under normal conditions, and the water resistance (after immersion at 20°C for 30 minutes) is 1.1 kg/25 mm, indicating excellent water resistance. Comparative Example 2 A composition was prepared in the same manner as in Example 4, except that the aqueous dispersion ( ) obtained in Experimental Example 3 was replaced with the aqueous dispersion ( ) obtained in Experimental Example 2. Hydroxyl group/isocyanate group of PVA added after polymerization = 5.7 (mole ratio) A polyester web was impregnated with this composition to obtain a nonwoven fabric. The tensile strength of this nonwoven fabric was 2.0 kg/25 mm under normal conditions, and the water resistance strength was 0.5 kg/25 mm. Example 5 100 parts of the aqueous dispersion () obtained in Experimental Example 3 was mixed with isophorone diisocyanate (IPDI), which was blocked with phenol. aqueous dispersion (solids concentration 30%, effective NCO content
6.15%). Hydroxyl group/isocyanate group of PVA = 2.6 (molar ratio) Six sheets of rayon web (basis weight 15 g/m ² ) were layered and immersed in a solution prepared by adding water to the above composition to adjust the solid content concentration to 5%, The fibers were squeezed with a mangle so that the resin content was 20% per fiber weight, dried at 60°C for 60 minutes, and then heat-treated at 150°C for 3 minutes. The tensile strength of the obtained nonwoven fabric is 2.8 kg/
25mm, water resistance strength (20℃, after 30 minutes immersion in water) is 1.6
Kg/25mm and has excellent water resistance. Example 6 Instead of the aqueous blocked isocyanate dispersion used in Example 5, a blocked isocyanate obtained by blocking methanol with xylidene diisocyanate (XDI) was used.

A rayon nonwoven fabric was obtained in the same manner as in Example 5, except that 5 parts of an aqueous dispersion of the formula (solid concentration 25%, effective NCO content 8.4%, average particle size 0.7μ) was used. PVA hydroxyl group/isocyanate group = 1.93 (mole ratio) The tensile strength of the obtained nonwoven fabric was 2.9Kg/25mm,
Water resistance (20℃, after 30 minutes immersion) is 1.5Kg/25mm
It showed good water resistance.

Claims (1)

[Scope of Claims] 1. An aqueous dispersion of ethylene-vinyl acetate copolymer (A) obtained by an emulsion copolymerization reaction using a water-soluble polyvinyl alcohol-based polymer as a protective colloid, and two copolymers in one molecule. An aqueous dispersion of a blocked isocyanate compound obtained by blocking a polyisocyanate compound having the above isocyanate groups with a compound selected from alcohols, phenols, oximes, mercaptans, amides, imides, and lactams; or an aqueous solution (B) of a blocked isocyanate compound obtained by blocking a polyisocyanate compound with an acidic sulfite, and the molar ratio of the isocyanate groups in (B) to the hydroxyl groups of polyvinyl alcohol in (A) is A composition having crosslinking properties, characterized in that the hydroxyl group/isocyanate group of polyvinyl alcohol is 1/0.05 to 1/1 (molar ratio).