JPS6342663B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to crosslinkable compositions. More specifically, water-soluble polyvinyl alcohol polymer (hereinafter referred to as
An aqueous dispersion of a reaction product of a polyisocyanate compound and an ethyleneimine compound is added to an aqueous dispersion of ethylene-vinyl acetate copolymer (A) obtained by an emulsion copolymerization reaction using PVA (simply abbreviated as PVA) as a protective colloid. liquid (B) is added, and the molar ratio of the aziridine groups in the (B) to the hydroxyl groups of the polyvinyl alcohol in the (A) is hydroxyl groups of polyvinyl alcohol/aziridine groups = 10
/1 to 1/1 (molar ratio). Conventionally, urea resins such as melamine-urea cocondensate resins and phenol resins are widely used in adhesives, textile processing agents, and pulp board processing agents because they are inexpensive, have good adhesive properties, and have good water resistance. Hygiene problems arise due to formalin generated during the reaction, 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. 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. Furthermore, when a system of isocyanate and a functional group such as a hydroxyl group or an amide group is used in an aqueous system, the pot life is short and there are many problems. JP-A-53-33251 proposes a method of using blocked isocyanates as a method of prolonging the pot life. In this method, a crosslinking reaction system is used between an aqueous dispersion of an ethylene-vinyl acetate multi-component copolymer obtained by copolymerizing a vinyl monomer having a hydroxyl group or an amide group, and a blocked isocyanate, but the pot life is certainly improved. This is because the reaction temperature is high and the copolymerization reactivity ratio between the vinyl monomer having hydroxyl groups and amide groups described in the specification of the patent and ethylene and vinyl acetate is different, making it difficult to efficiently introduce these functional groups. However, it is difficult to obtain a large crosslinking effect. However, the present inventors pursued an efficient crosslinking method for an aqueous dispersion of ethylene-vinyl acetate copolymer, which is flexible and has excellent adhesive properties, and as a result of extensive research, we developed an emulsion copolymer using PVA as a protective colloid. An aqueous dispersion (B) of a reaction product of a polyisocyanate compound and an ethyleneimine compound is added to an aqueous dispersion (A) of an ethylene-vinyl acetate copolymer obtained legally, and The molar ratio of the aziridine group in (B) to the hydroxyl group in polyvinyl alcohol in (A) is hydroxyl group in polyvinyl alcohol/aziridine group = 10
/1 to 1/1 (molar ratio), the composition exhibits excellent crosslinking reactivity at relatively low temperatures, that is, excellent water resistance, adhesion, and creep resistance, and has a long pot life in an aqueous system. We have completed the present invention by discovering that it exhibits excellent performance as an adhesive, textile processing agent, and pulp board processing agent without causing environmental hygiene problems such as formalin or organic solvents. 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 5.
40% by weight, vinyl acetate content is 95-60% by weight, preferably ethylene content is 8-30% by weight, and vinyl acetate content is emulsion copolymerized under pressure with ethylene such that the vinyl acetate content is 92-70% by weight. is 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 adhesiveness. PVA as a protective colloid used in producing 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.
In addition to using ~100 mol% of partially or completely saponified products, acrylonitrile,
After copolymerizing unsaturated carboxylic acids such as acrylamide, crotonic acid, acrylic acid, methacrylic acid, maleic acid, itaconic acid, and their alkyl esters with vinyl acetate and saponifying them, or producing PVA, sulfuric acid, phosphoric acid, Water-soluble so-called modified PVA or PVA derivatives such as those reacted with 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 in an aqueous dispersion obtained by polymerizing only in the presence of the above-mentioned activator and adding PVA after completion of polymerization, the crosslinking effect with isocyanate will be small. 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 (B) used in the present invention includes polyisocyanate compounds having two or more isocyanate groups in one molecule, such as ethyleneimine, methylethyleneimine, dimethylethyleneimine, ethylethyleneimine, methylethylethyleneimine, etc. An aqueous dispersion of the reaction product with an ethyleneimine compound is used. 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. The reaction between these polyisocyanate compounds and ethyleneimine compounds is usually carried out at room temperature or under cooling, using the ethyleneimine compound in an amount equivalent to or slightly in excess of the NCO group. The reaction product thus obtained is a cyclic structure of ethyleneimine.

It is considered to be a urea compound having the formula: The aqueous dispersion of the above reaction product is prepared by a conventionally known method of adding a solvent, water and an emulsifier and emulsifying the mixture. One of the features of the present invention is the use of an aqueous dispersion of the reaction product of polyisocyanate and ethyleneimine, that is, an aziridine compound. The crosslinking reaction system of the present invention is a reaction system between PVA and aziridine present on the surface of dispersed particles of ethylene-vinyl acetate copolymer, and both are in the form of an aqueous dispersion in which they are dispersed into minute particles. This is why micro-mixing is facilitated and crosslinking efficiency is improved. Forms other than aqueous dispersions cause the following disadvantages. For example, when an aziridine compound is in the form of an organic solvent solution, it is possible to mix it relatively microscopically by mechanically stirring with a large shearing force, but this is not practical because 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, it is important to use an aqueous dispersion of the reaction product of a polyisocyanate compound and an ethyleneimine compound, because even a small amount of the dispersion is added to produce a remarkable crosslinking effect. be. The reaction product of a polyisocyanate compound and an ethyleneimine compound has a relatively low crosslinking reaction temperature, and unlike conventional blocked isocyanate compounds, the blocking agent does not dissociate and remain behind during the crosslinking reaction. There is no need to worry about adverse effects on the physical properties of the composition or hygienic problems. The ratio of the reaction product of the ethylene-vinyl acetate copolymer aqueous dispersion to the polyisocyanate compound and the ethyleneimine compound is based on 1 mole of PVA hydroxyl groups present in the ethylene-vinyl acetate copolymer aqueous dispersion. The amount of aziridine group is 0.1 to 1 mole. If it is less than 0.1 mol, the crosslinking effect is small, and if it is more than 1 mol, the crosslinking effect hardly changes and is economically disadvantageous. Additives such as thickeners, plasticizers, and antifoaming agents that are normally 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 non-woven fabrics, texture improving agents for textiles, impregnating agents for pulp boards, etc.Flexibility, adhesive strength, solvent resistance, water resistance Used for applications that require high performance. As a method of using the crosslinkable composition of the present invention,
An aqueous dispersion (B) of a reaction product of a polyisocyanate compound and an ethyleneimine compound is added to an aqueous dispersion (A) of an ethylene-vinyl acetate copolymer containing PVA as a protective colloid. (B) for the hydroxyl group of polyvinyl alcohol
The molar ratio of aziridine groups in polyvinyl alcohol is hydroxyl group/aziridine group = 10
/1 to 1/1 (molar ratio), and after adjusting this to an appropriate viscosity, impregnate or coat the base material,
A common method is heat treatment at 100 to 190°C. In this case, if the heat treatment temperature is lower than 100°C, the crosslinking reaction rate will be slow and it will be necessary to take a long treatment time.
A high temperature of 190° C. or higher is not preferable because the base material undergoes significant thermal deterioration. Next, the present invention will be specifically explained with reference to Examples. Hereinafter, "parts" and percentages are expressed on a weight basis unless otherwise specified. 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 and then PH
Add and mix 0.5 parts of dibasic sodium phosphate and 10 parts of vinyl acetate as adjusting agents, and then add ethylene at a pressure of 40 kg/cm ²
Press in until the At an internal temperature of 65° C., 30 parts of a 2% potassium persulfate aqueous solution is added to initiate polymerization, and 67 parts of vinyl acetate is 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 concentration of 51.5%, a viscosity of 2200 cp, a pH of 4.5, and an ethylene content of 24.3%. Experimental Example 2 Preparation of an aqueous dispersion of ethylene-vinyl acetate copolymer () without using PVA 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 % aqueous solution of potassium persulfate 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°C, 30 parts of a 20% aqueous solution of PVA with a degree of polymerization of 500 and a degree of saponification of 88 mol% was added. The resulting aqueous dispersion had a solids content of 48.8% and a viscosity of
It was 980 cp and had an ethylene content of 22.5%. Example 1 In 100 g of an aqueous ethylene-vinyl acetate copolymer dispersion () obtained by emulsion copolymerization using PVA as a protective colloid in Experimental Example 1, methylene bis(4 5 g of an aqueous dispersion (solids content 25%, aziridine group content 6.4%) of the reaction product of phenyl isocyanate (MDI) and ethyleneimine are added. PVA hydroxyl group/aziridine group = 7.7 (molar ratio) The above composition was stable for two days at room temperature without any thickening phenomenon observed. Add water to the above composition to make 25%
Pulp board (basis weight
600g/m ² ) and squeezed with a mangle to impregnate the pulp board with solid content of 30%. Then, after pre-drying for 2 minutes at 40℃ using an infrared lamp, further
A pulp board with good texture was obtained by drying in a hot air dryer at 140°C for 30 minutes. The tensile strength 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) is 32.0.
Kg/15mm, 19.0Kg/15mm, and the water resistance is greatly improved compared to the pulp board before resin impregnation and the aqueous dispersion () alone (Table 1).

【table】

[Table] Example 2 To 100 g of the aqueous dispersion obtained in Experimental Example 1, 10 g of the aqueous dispersion of the reaction product of MDI and ethyleneimine used in Example 1 was added. PVA hydroxyl group/aziridine group = 3.8 (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 soaked in a stack of six sheets, 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 texture of the obtained nonwoven fabric was good, the tensile strength was 2.0 kg/25 mm under normal conditions, and the water resistance strength (after immersion at 20° C. for 30 minutes) was 1.3 kg/25 mm, indicating that it had sufficient water resistance. Example 3 To 100 g of the aqueous dispersion obtained in Experimental Example 1, 7 g of the aqueous dispersion of the reaction product of MDI and ethyleneimine used in Example 1 was added to obtain a composition. PVA hydroxyl group/aziridine group = 5.6 (mole ratio) 140g/
Apply a coating amount of 2 m ² and attach a 300μ thick soft vinyl chloride sheet. After air drying, it was hot pressed at 120°C for 1 minute and the 180° peel strength was measured. Under normal conditions
5.8Kg/25mm (wood breakage rate 100%), 5.3Kg/25mm (wood breakage rate 100%) 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/aziridine group of PVA added after polymerization = 5
.1 (molar ratio) The composition was used to bond plywood/soft vinyl chloride sheet. Normal adhesive strength is 3.3Kg/25mm
(Shallow wood damage), and the water resistant adhesive strength was 1.4Kg/25mm. The adhesion strength of the aqueous dispersion () alone without the addition of the reaction product of MDI and ethyleneimine is normal and water resistance is 3.0Kg/25mm and 0.9Kg/25mm, respectively.
Therefore, no significant improvement effect was observed in this regard. Experimental Example 3 Preparation of ethylene-vinyl acetate copolymer aqueous dispersion (): 1 mol% itaconic acid was copolymerized in the same autoclave as used in Experimental Example 1, with a degree of polymerization of 500 and a degree of saponification of 85 mol%. 2 parts of modified PVA and 2 parts of nonionic activator (Noniball 400: manufactured by Sanyo Chemical)
Dissolve 1 part and 70 parts of water. Then vinyl acetate 80
and 0.2 parts of dibasic sodium phosphate, a PH adjuster, were added and mixed, and ethylene was introduced under pressure to 45 kg/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 and tartaric acid were continuously added at 12 parts each over 5 hours during the polymerization. The resulting aqueous dispersion had a solid concentration of 50.8%, a viscosity of 250 cp (centipoise), a pH of 5.1, and an ethylene content of 20.5%. Example 4 A reaction product of hexamethylene diisocyanate (HDI) and ethyleneimine was dispersed in 100 g of the aqueous ethylene-vinyl acetate copolymer dispersion () obtained in Experimental Example 3 with a particle size of about 0.6μ. Aqueous dispersion (solid content 25%, aziridine group content 11.8%)
Add 5g of. PVA hydroxyl group/aziridine group = 1.4 (molar ratio) Add water to the above composition to adjust the solid content concentration to 5%, and add a polyester web (basis weight 15 g/m ² ).
The fibers were soaked in six layers, 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 texture of the obtained nonwoven fabric was good, the tensile strength was 1.85 Kg/25 mm under normal conditions, and the water resistance strength (after immersion at 20°C for 30 minutes) was 1.30 Kg/25 mm, indicating excellent water resistance. Comparative Example Same as Example 4 except that the aqueous ethylene-vinyl acetate copolymer dispersion () obtained in Experimental Example 2 was used instead of the aqueous ethylene-vinyl acetate copolymer dispersion () obtained in Experimental Example 3. A composition was similarly prepared. Hydroxyl group/aziridine group of PVA added after polymerization = 3
.8 (molar ratio) A polyester web was impregnated with the composition to obtain a nonwoven fabric. The tensile strength of the nonwoven fabric is 2.1Kg/
25mm, and the water resistance was 0.5Kg/25mm. Example 5 Instead of the aqueous dispersion of the reaction product of methylene bis(4-phenyl isocyanate) (MDI) and ethyleneimine used in Example 1, a reaction product of tolylene diisocyanate (TDI) and methylethyleneimine was used. Impregnation of the pulp board was carried out in the same manner as in Example 1, except that 5 g of an aqueous dispersion (solids concentration 30%, aziridine group content 8.75%) of the following were added. PVA hydroxyl group/aziridine group = 5.7 (molar ratio) The tensile strength of this resin-impregnated pulp board in the normal state and in the wet state after immersion in water (1 hour immersion in water at 20°C) is 31.2Kg/15mm and 19.3Kg/15mm, respectively. It can be seen that the water resistance is greatly improved when compared with that of the pulp board before resin impregnation and with the aqueous dispersion () alone as shown in Table 1 above. Example 6 Instead of the aqueous dispersion of the reaction product of hexamethylene diisocyanate (HDI) and ethyleneimine used in Example 4, an aqueous dispersion of the reaction product of xylidene diisocyanate (XDI) and dimethylethyleneimine was used. A nonwoven fabric was obtained using a polyester web in the same manner as in Example 4, except that 5 g of (solid content: 30%, aziridine group content: 7.6%) was added. PVA hydroxyl group/aziridine group = 2.1 (molar ratio) The tensile strength of the obtained nonwoven fabric is 1.75 kg/
25mm, water resistance (after immersion at 20℃ for 30 minutes) is 1.25
Kg/25mm, indicating good water resistance.

Claims (1)

[Scope of Claims] 1. A polyisocyanate compound and ethyleneimine are added to 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. an aqueous dispersion (B) of a reactant with the system compound, and the molar ratio of the aziridine group in the (B) to the hydroxyl group of the polyvinyl alcohol in the (A) is hydroxyl group of the polyvinyl alcohol/ Aziridine group = 10
/1 to 1/1 (molar ratio).