JP2821444B2 - Non-woven fabric binder - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a self-crosslinkable binder used for producing a nonwoven fabric. It is known to use a self-crosslinkable copolymer obtained by emulsion copolymerization of ethylene, vinyl acetate and N-methylol compound as a binder in the production of textiles such as nonwoven fabrics. . [0003] However, the crosslinking agent generates free formaldehyde during the crosslinking reaction, which is not preferable in terms of safety, especially when a nonwoven fabric is used as a clothing material. As a measure against formaldehyde, a method of copolymerizing acrylamide (JP-A-59-187658) has been proposed, but its effect has not been sufficient. A method using a collecting agent in combination (Japanese Patent Publication No. Sho 30-30824) has also been proposed, but its use is limited because dicyandiamide, urea, guanidine salts and the like are used. [0004] An object of the present invention is to develop a binder for nonwoven fabric which generates a small amount of free formaldehyde. The inventors of the present invention have conducted intensive studies to solve the problems associated with the binder for non-woven fabrics. As a result, when acrylamide- modified polyvinyl alcohol is used as a protective colloid, free formaldehyde is generated. The inventors have found that the amount is low and completed the present invention. That is, the acrylamide content of the present invention is 1 to
Acrylamide with a saponification degree of 85 mol% or more at 10% by weight
1 to 5 parts by weight of modified polyvinyl alcohol, 0.5 to 10% by weight of an N-methylol compound having a composition of 5 to 30% by weight of ethylene, N-methylol acrylamide and / or N-methylol methacrylamide, and vinyl acetate 60 According to a binder for a nonwoven fabric comprising 100 parts by weight of an N-methylol compound-ethylene-vinyl acetate copolymer in an amount of up to 94.5% by weight, the amount of free formaldehyde generated can be greatly reduced. [0007] The N-methylol compound-ethylene-vinyl acetate copolymer, which is a self-crosslinkable copolymer used in the nonwoven fabric binder of the present invention, has an ethylene content of 5 to 30% by weight. If the ethylene content is less than 5% by weight, the flexibility is insufficient, and an appropriate texture cannot be obtained for the nonwoven fabric product. On the other hand, if it exceeds 30%, the strength of the nonwoven fabric product is reduced. The content of the N-methylol compound composed of N-methylolacrylamide and / or N-methylolmethacrylamide is 0.5 to 10% by weight.
If it is less than 0.5% by weight, sufficient strength of the nonwoven fabric product cannot be obtained, while if it exceeds 10% by weight, the amount of free formaldehyde generated increases. The amount of acrylamide- modified polyvinyl alcohol used as a protective colloid is preferably 1 to 5% by weight (based on the solid content of the copolymer). If the amount is less than 1% by weight, the effect of suppressing formaldehyde generation is not sufficient, while if it exceeds 5% by weight, the viscosity of the self-crosslinkable copolymer increases remarkably. The acrylamide content in the acrylamide- modified polyvinyl alcohol is 1 to 10% by weight. If it is less than 1% by weight, the effect of suppressing formaldehyde generation is not sufficient, while if it exceeds 10% by weight, the protective colloid property is poor. The degree of saponification is at least 85 mol%. 85
If it is less than mol%, the protective colloid properties are poor. The present acrylamide- modified polyvinyl alcohol can be used as a protective colloid (eg, hydroxyethylcellulose, methylcellulose, etc.), a nonionic surfactant (eg, polyoxyethylene condensate, etc.) and an anionic surfactant (eg, polyoxyethylene cellulose) commonly used in emulsion polymerization. For example, alkylbenzene sulfonate). The acrylamide- modified polyvinyl alcohol can be obtained as a commercial product or can be produced by a known method. For example, vinyl acetate and acrylamide may be copolymerized by using azobisisobutyronitrile or the like as an initiator to obtain a vinyl acetate-acrylamide copolymer, or an arbitrary amount of acrylamide may be dissolved in methanol and continuously dissolved during polymerization. Add and homogenize. After removing the unreacted monomer in the methanol solution of the obtained polyvinyl acetate-acrylamide copolymer, acrylamide- modified polyvinyl alcohol can be obtained by adding an alkali not to saponify acrylamide and subjecting it to alcoholysis. As the emulsion polymerization method, a known method can be used. The polymerization conditions are not particularly limited, but generally the polymerization temperature is 20 to 80 ° C. and the polymerization pressure is 10 to 90 kg / cm 2.
Is used. In order to produce a nonwoven fabric using the self-crosslinkable copolymer nonwoven fabric binder obtained by the above method, unbonded or prebonded webs obtained by a wet or dry method are used. It is immersed in the binder, or the binder is attached by a method such as spraying, and dried and heat-treated. [0014] If necessary, an antifoaming agent, a pigment, a water repellent, a foaming agent, and a dispersing agent can be added to the binder, and the binder can be used in combination with a known binder such as SBR. The heat treatment is carried out at 100 to 200 ° C., preferably at 1 to 200 ° C.
A treatment at a temperature of 30 to 160 ° C. for 1 to 15 minutes is preferable,
If necessary, a crosslinking aid may be used in combination. As the crosslinking aid, mineral acids, organic acids and acid salts are used, and specifically, ammonium chloride, magnesium chloride, ammonium nitrate, maleic anhydride, alkanolamine and the like are used. According to the present invention, a binder for nonwoven fabric having a low free formaldehyde content can be obtained. The present invention will be specifically described below with reference to examples. Example 1 Production Example of Binder for Nonwoven Fabric 2650 g of pure water, 2850 g of vinyl acetate, Pluronic F-88, F-68 and L-64 (manufactured by Asahi Denka Kogyo Co., Ltd.) 30 g each of polyoxyethylene / polyoxypropylene block copolymer), 45 g of hydroxyethyl cellulose (manufactured by Fuji Chemical Co., Ltd.), ammonium of hytenol N-17 (polyoxyalkyl (or allyl) sulfate manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Salt) 2
2.5 g, 90 g of acrylamide- modified polyvinyl alcohol (acrylamide content: 5% by weight, saponification degree: 90 mol%), and 12 g of sodium acetate were charged. The internal temperature is raised to 70 ° C. and ethylene is reduced to 50 k.
g / cm2. 0.6 g of ammonium persulfate was added to initiate polymerization. The internal temperature was kept constant by adjusting the temperature of the jacket. N-methylolacrylamide (150 grams) was dissolved in 350 milliliters of water and dispensed continuously over 6 hours from the start of the polymerization. After 10 hours, the contents were cooled and the contents were taken out. The content is a stable emulsion with a small amount of coarse particles.
6% by weight, viscosity 2120 cps, modified with acrylamide
3 parts by weight of polyvinyl alcohol and polymer composition of acetic acid
76% by weight of vinyl unit, 19% by weight of ethylene unit
%, N-methylol acrylamide unit 5% by weight
Certain N-methylol compounds-ethylene-vinyl acetate copolymer
The mixture contained 100 parts by weight. Comparative Example 1 The charged amounts of pure water and vinyl acetate were 2440 g each,
2760 g, acrylamide modified as protective colloid
Without the use of sex polyvinyl alcohol was dissolved N- methylol acrylamide 150 g and acrylamide 90 g of 560 ml of water, except that continuously Bun添over 6 hours from the polymerization initiation, Example 1
The polymerization was carried out in the same manner as described above. [0020] After 10 hours, was taken out The cooled contents are coarse less stable emulsion, solid content 50.5 wt%, a viscosity 2800Cps, Akurirua
It does not contain amide- modified polyvinyl alcohol and its polymer composition is 74% by weight of vinyl acetate unit, 18% by weight of ethylene unit, 3% by weight of acrylamide unit,
The amount of the methylol acrylamide unit was 5% by weight. Example 2 The binder prepared by the method of Example 1 was replaced with Toyo Filter Paper No.
2 (120 g / m2) so as to have an impregnation ratio of 25% by weight, air-dried, and then heat-treated at 140 ° C for 5 minutes. The performance of the impregnated paper is shown in the table. Examples 3 and 4 and Comparative Examples 2 and 3 Example 1 except that the amount of N-methylolacrylamide was changed.
The binders having the compositions shown in the table prepared in the same manner as in Example 1 were evaluated. Examples 5, 6, and 7 The procedure of Example 2 was repeated except that N-methylol methacrylamide was used instead of N-methylol acrylamide.
Production and evaluation were performed in the same manner as in Examples 3 and 4. Examples 8, 9, and 10 The same procedures as in Examples 2, 3 and 4 were carried out except that acrylamide- modified polyvinyl alcohol having an acrylamide content of 9% by weight and a saponification degree of 95 mol% was used. Examples 11 and 12 The same binders as those used in Examples 2 and 5 were impregnated into a 100% rayon web (basis weight 100 g / m2) so that the impregnation rate was 35% by weight. After air drying, heat treatment was performed at 140 ° C. for 5 minutes. Comparative Examples 4 and 5 Binders having the compositions shown in the table prepared in the same manner as in Example 1 except that the ethylene content was changed by changing the ethylene pressure were evaluated. Comparative Examples 6 and 7 Binders prepared in the same manner as in Example 1 except that the amount of acrylamide- modified polyvinyl alcohol was changed were evaluated. Comparative Example 8 The binder prepared by the method of Comparative Example 1 was evaluated in the same manner as in Example 2. Comparative Example 9 A binder prepared in the same manner as in Comparative Example 1 except that the amount of N-methylolacrylamide was changed was evaluated. [Table 1] Measurement Method (1) Tensile Strength at Drying Cut the impregnated paper into a size of 15 × 150 cm and use a tensile tester IS-500 manufactured by Shimadzu Corporation at a tensile speed of 200 mm /
Measured at a distance between chucks of 100 mm. (2) Tensile strength when wet The impregnated paper was immersed in water at 20 ° C for 2 hours, and the strength was measured in the same manner as (1). (3) Measured by a texture handling test. The case where the test piece was bent with almost no resistance was defined as “good”. (4) Amount of free formaldehyde The amount of formaldehyde was quantified based on the Ministry of Health and Welfare Ordinance No. 34 (detection limit: 0.1 ppm). (5) State of Binder 100 g of the binder was put into a beaker, and the state was observed by stirring with a glass rod. "Good" when stirring is possible with little resistance, "Slightly thickening" when there is some resistance,
The larger the resistance, the higher the viscosity.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ identification symbol FI C08F 210: 02) (C08L 31/04 29:04) (58) Investigated field (Int.Cl. ⁶ , DB name) C08L 31 / 04 C08L 29/04 C08F 218/08

Claims (1)

(57) [Claims] 1 to 5 parts by weight of acrylamide- modified polyvinyl alcohol having an acrylamide content of 1 to 10% by weight and a degree of saponification of 85 mol% or more, and a composition of ethylene 5 to 3
0% by weight, 0.5 to 10% by weight of an N-methylol compound composed of N-methylol acrylamide and / or N-methylol methacrylamide, and 60 to 60% by weight of vinyl acetate
A nonwoven fabric binder comprising 100 parts by weight of 94.5% by weight of an N-methylol compound-ethylene-vinyl acetate copolymer.