JPS63175151A - Binder for nonwoven fabric excellent in solvent resistance - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improved binder for nonwoven fabrics, and more particularly, to a binder for nonwoven fabrics that can provide nonwoven fabrics with excellent solvent resistance.

[Conventional technology and its problems]

There are several methods for binding the fibers of dry-processed non-woven fabrics: using a binder (binding agent), attaching the flag fibers with thermal FI4i, and mechanically intertwining the field fibers. It is most widely used because it can be applied to nonwoven fabrics. Most of the binders used are mainly composed of an aqueous dispersion of polymer particles called latex or emulsion, and the types of polymers include acrylic, vinegar-based copolymers, and S.
BR type, NBR type, etc. are used.

One of the most important properties required of nonwoven fabrics is solvent resistance, and the improved performance of latex has a big impact on this! #
give.

For example, in nonwoven fabrics for clothing cores, latex cannot withstand dry cleaning unless its solvent properties are sufficient. Furthermore, even in nonwoven fabrics used for general industrial materials and miscellaneous goods, the solvent resistance required for each use is largely influenced by the performance of the latex.

One method to improve this solvent resistance is to copolymerize the latex used as a binder with a functional monomer such as N-methylol (meth)acrylamide, which has crosslinking reactivity, or to copolymerize water-soluble trimethylol. There is a method of forming a cross-linked structure in the latex polymer in the heat treatment process of the nonwoven fabric by using a polyfunctional thermosetting resin such as melami/oblast at the time of processing.

However, these methods cannot introduce a large amount of crosslinking components, as this reduces the chemical stability of the latex, and in order to obtain a sufficient effect, they require long periods of time at high temperatures. In the actual nonwoven fabric manufacturing process, which requires consideration of productivity since heat treatment is involved, satisfactory effects have not been obtained.

For this reason, NBR (acrylonitrile-butadiene rubber) latex is used practically when a high degree of solvent resistance is required. The reason for this is that NBR has a relatively high acrylonitrile content compared to other latexes.

Because di) I) group (-C
This is because the high nitrile group content gives the film high resistance to oils and organic solvents, that is, solvent resistance.

However, when the ratio of acrylonitrile in NBR latex is increased in order to obtain higher solvent resistance, the emulsion polymerization reaction during production does not proceed and becomes unstable, and the resulting NBR latex also has poor mechanical stability. Therefore, it has the disadvantage that it cannot withstand the impregnation process of nonwoven fabric.

For this reason, in recent years, due to the diversification of nonwoven fabric uses and the sophistication of required performance, there has been a demand for a binder with even better solvent resistance than conventional NBR. It wasn't.

The present invention was made in consideration of the above-mentioned conventional circumstances, and aims to improve the insufficient solvent resistance and mechanical stability of NBR latex as a conventional binder for nonwoven fabrics. It is.

[Means for solving problems]

The present inventors investigated how to introduce as many nitrile groups into polymer molecules in order to develop a latex as a binder for nonwoven fabrics that has better solvent resistance and mechanical stability than conventional NBR latex. I found out that it has a high level of solvent resistance. In order to achieve this, the weight swelling ratio of the latex film with respect to toluene must be 200% or less, and in order to satisfy this condition, a monomer composition containing 17% by weight or more of nitrile groups in the polymer molecule must be used. I found out that it has to be latex. As a result of further intensive research, surprisingly, polymerization stability was significantly improved by using methacrylonitrile as part or all of the monomer to introduce a nitrile group, and the resulting latex also improved. It was discovered that the processed nonwoven fabric has extremely high mechanical stability and an extremely high degree of solvent resistance that could never be obtained with conventional NBR latex, leading to the completion of the present invention.

That is, the present invention contains 35 to 60% by weight of butashun, 5 to 60% by weight of methacrylotrile, and ethylenic incompatibility/I/
A monomer mixture consisting of 1 to 8% by weight of fonic acid and 0 to 59% of other ethylenic monomers copolymerizable with these monomers is emulsion polymerized, and the nitrile group (-( The present invention provides a binder for nonwoven fabrics that uses latex with a ratio of 17''M ratio (=N) or more of 17''M or more and has excellent solvent resistance.

Butadiene used in the present invention is a monomer that is necessary to give flexibility to the latex film and to facilitate the formation of a binder film at normal drying temperatures in the drying process of nonwoven fabric processing. It is used in an amount of 35 to 60% by weight based on the monomer.

If the amount of butadiene used is less than 35% by weight, the obtained latex film will be brittle and the film will not be formed sufficiently at room temperature, so a dry powder will be produced in the nonwoven fabric impregnation process, and the impregnation will It interferes with work. Also,
If the amount of butadiene used exceeds 60% by weight, the resulting latex film will have poor solvent resistance, making it impossible to achieve the object of the present invention. The methacrylonitrile used in the present invention not only imparts solvent resistance to the latex film, but also
It is a monomer necessary to increase the cohesive force of the film, and is an essential monomer to obtain the high degree of solvent resistance that is the objective of the present invention. ~60% heavy duty.

If the amount of methacrylonitrile used is less than 5% by weight, even if acrylonitrile is used in combination and the nitrile content in the polymer is tt-1711tt% or more, the reaction during emulsion polymerization will be difficult to proceed, the polymerization stability will be poor, and the nonwoven fabric will deteriorate. Poor mechanical stability during impregnation work and poor solvent resistance. Furthermore, if the amount used exceeds 60% by weight, the film forming properties of the latex at room temperature will decrease, resulting in a decrease in workability in the nonwoven fabric impregnation process, as described above.

Ethylenically unsaturated carboxylic acids used in the present invention include acrylic acid, methacrylic acid, crotonic acid, maleic acid and its anhydride, fumaric acid, itaconic acid, and unsaturated dicarboxylic acid monoalkyl esters, such as monomethyl maleate. Monoethyl fumarate, mono-n itaconate
Ethylenically unsaturated carboxylic acids such as -butyl can be used in an amount of 1 to 8% by weight based on the total monomers.

Ethylenically unsaturated carboxylic acid is a monomer component necessary to improve the adhesion of the latex film to the fibers and the mechanical stability of the latex, and its usage amount is based on the total monomer. If the amount is less than 1% by weight, these effects cannot be obtained. In addition, if the amount used exceeds 8% by weight,
The latex becomes highly viscous, making it impossible to uniformly impregnate the nonwoven fabric.

Other ethylenically unsaturated monomers that can be copolymerized with butadiene, methacrylonitrile, and ethylenically unsaturated carboxylic acids used in the present invention include, in addition to acrylonitrile, methyl acrylate, methyl methacrylate, ethyl acrylate, and methacryl. Ethyl acid, propyl acrylate, globyl methacrylate, butyl acrylate, butyl methacrylate, pentyl acrylate, pentyl methacrylate, hexyl acrylate, hexyl methacrylate, heptyl acrylate, heptyl methacrylate, octyl acrylate, octyl methacrylate , acrylic acid alkyl esters and methacrylic acid alkyl esters, such as octadecyl acrylate, octadecyl methacrylate, etc.; Unsaturated aromatic monomers; vinyl esters such as vinyl acetate, vinyl propionate, etc.; vinylidene hasides such as vinylidene chloride, vinylidene bromide, etc.: 2-hydroxyethyl acrylate, 2-hydro-dipropyl acrylate, Hydroxyalkyl esters of ethylenically unsaturated carboxylic acids, such as 2-hydroxyethyl methacrylate, etc.: Glycidyl esters of ethylenically unsaturated carboxylic acids, such as glycidyl acrylate, glycidyl methacrylate, etc., and acrylamide, methacrylamide, N-
Examples include radically polymerizable monomers such as methylol acrylamide, N-methylol methacrylamide, N-butoxymethyl acrylamide, and diacetone acrylamide.

The latex of the present invention has the above-mentioned Butashun 55-60.
weight %, methacrylonitrile 5-60 Jj[%, ethylenically un9-phase carboxylic acid 1-8i weight %, and other ethylenically unsaturated monomers copolymerizable with these monomers 0-59
M! %, but if the proportion of methacrylonitrile used is small, a nitrile group-containing monomer such as acrylonitrile may be used as other ethylenically unsaturated monomer to form a latex polymer. It is necessary that the nitrile group C content is 17% by weight or more.

The latex of the present invention is prepared by polymerizing the above monomer mixture in an aqueous medium by a conventional emulsion polymerization method. For example, a monomer mixture is emulsified and dispersed in water in the presence of an anionic or nonionic emulsifier, and a free radical generating catalyst,
For example, KPS (K, S, O,), AP S ((NH
4) Emulsion polymerization may be carried out preferably at 40°C to 90°C using an aqueous catalyst such as tstoa), hydrogen peroxide, or an oil catalyst such as t-butyl hydroperoxide or cumene hydroperoxide.

Furthermore, in the present invention, additives commonly used in emulsion polymerization, such as chain transfer agents, ethylenediaminetetraacetic acid for the purpose of polymerization stabilization and buffering effects, etc. may be used as necessary.

The latex of the invention is concentrated to the required solids content, for example by methods such as stripping.

The obtained latex has a pH of 3 to 7 and a viscosity of 60 to 100.
The pH is about 0 cps, and more preferably the pH is adjusted to 8 to 1o with an alkaline solution to improve stability.

〔Effect of the invention〕

When the latex of the present invention thus obtained is used as a binder to process a nonwoven fabric, the nonwoven fabric has extremely excellent solvent resistance and can have a wide range of textures depending on the application, from extremely soft to hard. It is ideal as a nonwoven fabric for clothing and materials. It also has good stability in terms of impregnability and sprayability.

Next, the present invention will be specifically explained with reference to Examples. In addition,
The number of copies and percentages shown in the text indicate parts by weight and weight percentages, respectively.

In addition, the aggregate formation rate and mechanical stability of the latex in Examples were measured by the following methods.

〔Measuring method〕

0+ Aggregate formation rate (%) Latex 1009 after the completion of the polymerization reaction was passed through a 200 mesh cloth, and the weight of P remaining after drying at 120°C for 1 hour was divided by the solid weight of the total latex. Values are expressed as percentages.

(2) Mechanical stability Using a Marlon type mechanical stability tester, 50 g of latex was rubbed at a load of 10 kl/ and a rotation speed of 300 rpm for 10 minutes, and the resulting aggregates were dried at 120°C for 1 hour. The value obtained by dividing the remaining weight by the solid weight of the latex was expressed as a percentage.

Examples 1 to 4 Raw materials having the composition shown in Table 1 were charged into a nitrogen-substituted autoclave equipped with a stirrer, and emulsion polymerization was carried out with stirring at Fm'':E1°C until the polymerization rate reached 959 or more. After removing monomer by distillation, 25% ammonia water is added to adjust the pH to 8-9, and if necessary, ion-exchanged water is added to reduce the solid content to 39.0-4tO%.
latex A, B.

The critical polymerization to obtain C and D proceeded stably until the target polymerization rate of 95% or more was reached, and as shown in Table 1, the amount of aggregates generated during the polymerization was extremely low. It was small.

The viscosity of the obtained latex was low, and the mechanical stability was also extremely good.

Comparative Examples 1 and 2 Raw materials having the compositions shown in Table 1 were charged in the same manner as in Examples 1 to 4, and emulsion polymerization was carried out at 50° C. with stirring, aiming at a polymerization rate of 95% or more. Next, in the same manner as in Examples 1 to 4, demonomer, pH adjustment, and solid content adjustment were performed to adjust the pH.
8-9, a latex with a solid content of 390-4 tO% was obtained.

The results are shown in Table 1. In Comparative Example 1, in which methacrylonitrile was not used, the polymerization was completely unstable, and 8 hours after the start of polymerization, the polymer particles during polymerization agglomerated, making it impossible to obtain latex. Ta.

Furthermore, in Comparative Example 2 in which the amount of methacrylonitrile used was small, the polymerization reaction was difficult to proceed, and even if the reaction was continued for as long as 20 hours, the polymerization light was extremely low at 93.8%. Furthermore, the number of aggregates generated during polymerization was much larger than in Examples 1 to 5, which are examples of the present invention, indicating that the polymerization was unstable. Furthermore, the obtained latex E had extremely poor mechanical stability.

From the above results, it can be seen that in the case of a monomer composition containing less than 5% methacriconitrile and a high nitrile group content, stable emulsion polymerization is possible, but the obtained latex is also unstable.

Comparative Examples 3 to 6 Raw materials having the compositions shown in Table 1 were charged in the same manner as in Examples 1 to 4, and emulsion polymerization was carried out at 50° C. with stirring until the polymerization light reached 95% or more. Next, in the same manner as in Examples 1 to 4, demonomer, pH adjustment, and solid content adjustment were performed to adjust the pH.
A latex with a solid content of 320-410% was obtained.

The results are shown in Table 1. In Comparative Example 6, which contained less ethylenically unsaturated carboxylic acid, the mechanical properties of the 2-tex were extremely poor.

Furthermore, in Comparative Example 4, which contains a large amount of ethylenically unsaturated carboxylic acid, the viscosity of the latex was extremely high at 3,620 cps. , dried at 25°C for 2 days to obtain a film thickness of a3 to 15WII.
A dry film was obtained. Next, this film was heat-treated at 140°C for 10 minutes in a hot air circulation dryer, then immersed in toluene and allowed to stand at 25°C for 4 days, and the weight swelling ratio was calculated according to the following formula.

The results are shown in Table 2.Although they all swelled with toluene, the swelling rate remained below 200%.
The higher the nitrile group content, the better the solvent resistance.

Next, latex A, B, C, and D obtained in Examples 1 to 4 were each diluted with water to adjust the solid content to 12.5%, and after fC,
A polyester web with a basis weight of 309/m" was sandwiched between wire meshes and dipped in latex to allow the latex to penetrate into the web to observe the ease of penetration. After impregnation, the nonwoven fabric was mixed with latex using a mangle of rubber rolls/stainless steel rolls. (w
et)/fiber=32.5/100 (weight ratio) under certain conditions, and the presence or absence of latex aggregates on the wire mesh and mangle was determined. Next, after drying at 100° C. for 5 minutes, baking was performed at 150° C. for 1 minute to obtain a nonwoven fabric with latex solid content/@fiber=13/100 (weight ratio). Next, the nonwoven fabric interlining test method (JIS L-
1085), the morphological change of the nonwoven fabric in the dry cleaning strength test of the nonwoven fabric up to 3 cycles was evaluated according to the following criteria. In addition, the judgment criteria for morphological changes are: Class A, no change Class B, noticeable change Class 0, marked change As shown in Table 2, the stability of the latex during mangle drawing was good in all cases, and the dry cleaning strength of the nonwoven fabric was There was no morphological change due to the test.

Comparative Test Example Using the latex E-I obtained in Comparative Examples 2 to 6, the weight swelling ratio of the heat-treated film to toluene was measured in the same manner as in the test example. Next, the nonwoven fabric was processed in the same manner as in the test example, and the stability of the latex in mangle drawing and the morphological change in the dry IJ-ning strength test were investigated.

As shown in Table 2, the nitrile group content was 16.6.
% of latex I was heat-treated by toluene.
The f-swelling rate was high, and the dry cleaning strength of the processed nonwoven fabric was also poor.

Latex E with a methacrylonitrile content of 4% and latex F with an ethylenically unsaturated carboxylic acid content of 0.5% produced aggregates during mangle squeezing, resulting in significant
Stability was poor.

In addition, Latex G containing 10% of ethylenically unsaturated carboxylic acid had too high a viscosity, resulting in uneven penetration into the nonwoven fabric, and as a result, its dry cleaning strength was poor.

Latex H, which contains 36% butadiene, does not have the ability to form a film at room temperature (25°C), and as a result, powdery dry matter is generated at the end of the roll during mangle squeezing, and it falls into the impregnating liquid. Workability was significantly poor.

From the above results, it can be seen that a latex having a monomer composition and a nitrile group content outside the scope of the claims of the present invention is not suitable as a binder for a solvent-resistant nonwoven fabric.

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Claims (1)

[Claims] 1. 35-60% by weight of butadiene, 5-60% by weight of methacrylonitrile, 1-8% by weight of ethylenically unsaturated carboxylic acid, and 0-59% of other ethylenically unsaturated monomers copolymerizable with these monomers. Emulsion polymerization of a monomer mixture consisting of
A binder for nonwoven fabrics having excellent solvent resistance using latex with a proportion of C≡N) of 17% by weight or more.