JPH0192480A - Binder for nonwoven fabric - Google Patents

Abstract

PURPOSE: To obtain a binder for nonwoven fabric good in resin penetration into nonwoven fabrics and having high water resistance by blending a copolymer comprising isobutylene and an unsaturated dicarboxylic acid anhydride and having a specific molecular weight with a PVA. CONSTITUTION: This binder for nonwoven fabrics is obtained by blending a copolymer, produced by copolymerizing isobutylene with an unsaturated dicarboxylic acid anhydride (e.g. maleic anhydride) in the weight ratio of 1:(0.1-1.2) and having 50,000-170,000 average molecular weight, with a PVA and impregnating into a nonwoven fabric. The nonwoven fabric is suitable for roofing as it has high water resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a binder for nonwoven fabrics used in roofing base fabrics, and more specifically to a highly water-resistant polyvinyl alcohol binder. be.

(Prior Art) Normally, as a base fabric for roofing, a nonwoven fabric made of paper or synthetic fibers such as polyester, vinylon, polyethylene, etc. is widely used.

Due to its use, base fabrics for roofing must have high tensile strength, stress at 3% elongation, and high tear strength in order to ensure the waterproofness and durability of the roofing. is desired, and in many cases, treatment with a synthetic resin binder is performed for the purpose of improving the physical properties of the base fabric.

As binder resins, acrylic resins, urethane resins, epoxy resins, etc. are well known in order to meet the above physical properties, but these resins are relatively expensive and are usually used in asphalt roofing construction. At present, inexpensive polyvinyl alcohol resins are often used in view of cost.

(Problems to be Solved by the Invention) However, polyvinyl alcohol resin (hereinafter referred to as PVA), which has been conventionally used as a binder for nonwoven fabrics, has low water resistance (and is resistant to rainwater, etc.) even after heat treatment. Nine letters will be dissolved.

In products impregnated with asphalt pitch, it is inevitable that pinholes will occur because the air inside the nonwoven fabric cannot escape during manufacturing, and scratches may be made by mistake during construction. If the PVA penetrates further, the PVA will easily swell and dissolve, reducing the adhesive strength between the fibers and causing changes in the base fabric structure. Originally, the main function of roofing materials is to prevent water from penetrating and provide waterproof properties. This means that the construction will have to be redone because it will swerve.

For this reason, for roofing materials that require maximum durability for high-rise buildings and civil engineering works, we use not only materials with excellent base fabric performance, but also water-resistant adhesives such as epoxy resin 1 and urethane resin. Currently, those with superior performance are used.

Therefore, for these reasons, it is absolutely necessary for the PVA binder used in the roofing fabric to have improved water resistance. As a means for improving the water resistance of PVA, it is known that a saturated dicarboxylic acid or urea-melamine crosslinking agent is blended into PVA and the water resistance is improved through a crosslinking and curing reaction caused by heat. However, when a saturated dicarboxylic acid is blended with Pv8, the resin discolors due to heat treatment, the texture hardens, and peeling between base fabric layers is likely to occur, which is not preferable as a binder for a ruling nonwoven fabric. On the other hand, in the case of a urea-melamine crosslinking agent, formalin gas generated during processing deteriorates the working environment, which is not preferable in terms of workability.

(Means for Solving the Problems) The present inventors have arrived at the present invention as a result of intensive research to solve the above problems.

That is, in the present invention, the average molecular weight is 50,000 to 170.
The gist of this invention is a binder for nonwoven fabrics, which is characterized in that it is made by blending a copolymer of 000 isobutylene and an unsaturated dicarboxylic acid anhydride with polyvinyl alcohol.

The molecular weight of PVA used in the present invention is not particularly limited, but it is preferably one commercially available as a binder for ordinary fibers.1 A degree of polymerization of about 500 to 100 is preferred in terms of permeability and operability during resin processing. .

Next, the copolymer used in the present invention is composed of isobutylene and an unsaturated dicarboxylic acid anhydride.

For example, Japanese Patent Publication No. 49-6396 and Japanese Patent Publication No. 49-6
As known from Publication No. 832, precipitation polymerization is carried out in a solvent that has excellent solubility for the reaction monomer in the presence of an azo compound or peroxide as a catalyst and is insoluble for the resulting copolymer. obtained by Also,
The bonding mode may be so-called randomly bonded, isobutylene and unsaturated dicarboxylic anhydride bonded to a block, or a mixture of both.

The method of connection does not matter.

Examples of unsaturated dicarboxylic anhydrides include maleic anhydride,
Ethylenically unsaturated carboxylic acid anhydrides such as itaconic anhydride are used, with maleic anhydride being particularly preferred.

The copolymerization ratio of isobutylene and unsaturated dicarboxylic acid anhydride is preferably i:o and t~1.2 at a weight ratio of 1. If the isobutylene content exceeds the above range, it will become rubbery and the 1 elastic modulus will be low. Furthermore, when such a copolymer containing isobutylene is used as a crosslinking agent for Pv, it is necessary to increase the amount of the copolymer (2) in order to improve water resistance. on the other hand.

If the content of unsaturated dicarboxylic acid anhydride increases, it is not preferable because the main chain of isobutylene will break during the reaction. show. In addition, in the case of this blend, since there are many carboxyl residues, there is also the advantage that water resistance is improved even if the blended amount of the copolymer is reduced. In view of the molecular anti-cleavage crosslinking reaction and the physical properties of the compound, the copolymerization ratio of both is most preferably 1:1 (3 weight ratio).

Here, an example of a method for producing the copolymer of the present invention is as follows. When isobutylene and maleic anhydride are precipitated and copolymerized, isopropyl acetate or a mixture of ethyl acetate and tertiary-butanol is used as the polymerization reaction solvent, and a radical polymerization catalyst such as azobisiso-butyronitrile or benzoyl peroxide is used as the polymerization catalyst.
The amount of catalyst is 0.05 to 1.0 mol% based on maleic anhydride, 1 polymerization temperature 45 to 85℃, 1 polymerization pressure 3 to 5
kg/CI”.

It is obtained by carrying out the polymerization for 5 to 6 hours.

Furthermore, what is the mixing ratio of isobutylene and maleic anhydride?

In order to improve the utilization rate of maleic anhydride, it is preferable that the molar ratio of isobutylene to maleic anhydride is 1 or more. The amount of the 8-polymerization reaction solvent used is preferably such that the copolymer concentration is 10 to 30% by weight.

Next, the molecular weight of the copolymer of isobutylene and unsaturated dicarboxylic acid (hereinafter sometimes simply abbreviated as copolymer) used in the present invention is 50,000 to 1,700.
Must be 00. If the molecular weight is less than 50,000, sufficient improvement in water resistance is not observed, and in order to obtain a water resistance effect, it is necessary to increase the blending ratio with respect to PVA. However, when the above blending ratio is increased, the tensile strength and tear strength of the nonwoven fabric base layer decrease. On the other hand, when the molecular weight exceeds 170,000, the solution viscosity increases, the permeability into the base fabric decreases, and productivity deteriorates.

Next, regarding the blending ratio of PVA and copolymer, pv
It is preferably 5 to 20% with respect to
2% is optimal. When the blending ratio is less than 5%.

The improvement in water resistance is not significant, and on the other hand, if it exceeds 20%, the texture becomes hard and the water resistance reaches its peak, which is also disadvantageous from an economical point of view, which is not preferable.

(Function) A PVA-based binder with high water resistance can be obtained by blending a copolymer of isobutylene and an unsaturated dicarboxylic acid anhydride with a specific molecular weight into PVA. The present inventors explained the reason for this.

It is considered as follows.

By blending a copolymer of isobutylene and unsaturated dicarboxylic acid anhydride with PVA, the carboxyl residue bonds with the hydroxyl group of Pv^ by the heat during the first heat treatment, and the resin becomes three-dimensional due to a crosslinking reaction between molecular chains. Water resistance will improve.

Regarding this cross-linking reaction mechanism between molecular chains.

It is the same as urea-melamine resin and saturated dicarboxylic acid, which are conventional crosslinking agents for PVA. However, when the above conventional resins are used as crosslinking agents, the resins become discolored.

There are problems such as formalin odor. In addition, self-crosslinking products such as synthetic rubber Latinx resins and acrylic resins are commercially available, but they have few carboxylic acid residues and low crosslinking density.6 When used for the purpose of improving the water resistance of the PVA resin of the present invention. , it is necessary to increase the amount of the resin, which increases the cost. As described above, satisfying all of the resin coloration, operability, cost, water resistance, and tensile strength can only be achieved by blending an appropriate amount of the copolymer defined in the present invention with PVA. In other words, the copolymer of the present invention is composed of a copolymer having both flexibility and elasticity, and furthermore, by using maleic anhydride as the unsaturated dicarboxylic anhydride, the copolymer has an appropriate molecular weight that is favorable in terms of workability. A crosslinking agent containing many highly reactive carboxylic acid residues can be obtained in good yield. For this reason, it is possible to reduce the amount of PVA compounded compared to conventional PVA-based crosslinking agents, and it has been possible to improve the water resistance of PVA resin with a binder for nonwoven fabrics that does not cause thermal discoloration or formalin odor. .

(Example) The present invention will be specifically explained below using examples.

Note that the performance of the nonwoven fabric in Examples is as follows.

25 on a non-woven fabric with a basis weight of 140 g/m
PVA and PVA with constant solids concentration temperature adjusted to °C
2 cc of a mixture of the above and the copolymer was added dropwise, and the state of penetration was visually determined.

Evaluation criteria: O...--Good △... Normal The sample was boiled for 30 minutes, and the dissolution rate was determined from the change in weight after boiling.

■ Weight (3) Tensile strength 3 cm according to JTS L-1096 strip method
A sample piece of X 3Qcn+ was pulled at a speed of 2Qcm/min,
+ Determined using a tensile tester with a grip interval of 20 cm, n = 10
It is shown as the average value.

(4) Tear Strength A sample piece of 6.5 marks x 10 cm was measured using a pendulum type tester according to the JIS L-1096 pendulum method.

The average value of n=10 is shown.

Example 1 Using polyethylene terephthalate with an intrinsic viscosity of 0.69, a single yarn fineness of 3.1 d and a basis weight of 140 g was produced by the spunbond method.
/ m 2 A nonwoven fabric was produced by pressing with an embossing roll. As a binder for nonwoven fabric, a copolymer of isobutylene and maleic anhydride [Kuraray products, trade name: Kuraray Isoban 10] is used as a binder for 100 parts by weight of PVA with an average degree of polymerization of 1000 (hereinafter, 1 part by weight is simply referred to as part).
4. Copolymerization ratio 1:1 (weight ratio), average molecular weight 55,000
Using an aqueous dispersion (resin solid content: 20%) containing 15 parts, the nonwoven fabric was impregnated by dipping, and the squeezing rate was 1.
The liquid was removed using a mangle until the concentration was 00%. Then 10
After drying at 0°C for 5 minutes.

Heat treatment was performed at 170° C. for 7 minutes to obtain a nonwoven fabric for roofing. The performance of the obtained nonwoven fabric was determined and the results are shown in Table 1.

Examples 2 to 3 The polyethylene terephthalate spunbond nonwoven fabric of Example 1 was used, except that the amount of the copolymer of Example 2 relative to PVA was changed to 8 parts (Example 2) and 20 parts (Example 3). Resin processing was performed in accordance with Example 1 in all other respects to obtain a nonwoven fabric for roofing. The results are shown in Table 1.

Example 4 Practical I Using the polyethylene terephthalate spunbond nonwoven fabric of Example 1, a copolymer of isobutylene and maleic anhydride with a molecular weight of 170,000 [■Kuraray products, trade name: Kuraray Isoban 104 and Kuraray/Ha/11]
A nonwoven fabric for roofing was obtained by resin processing in the same manner as in Example 1 except that the mixed product (mixture ratio: 15:85) was changed to 8 parts to 100 parts of PVA. Results first
Shown in the table.

Examples 5 to 6 The polyethylene terephthalate spunbond nonwoven fabric of Example 1 was used, except that the amount of the copolymer of Example 4 relative to PVA was changed to 12 parts (Example 5) and 20 parts (Example 6). All other resin processing was performed according to Example 1,
A nonwoven fabric for roofing was obtained. The results are shown in Table 1.

Comparative Example 1 Using the polyethylene terephthalate spunbond nonwoven fabric of Example 1, a copolymer of isobutylene and maleic anhydride with a molecular weight of 190,000 [■Kuraray products, trade name: Kuraray Isoban 11O1 copolymerization ratio l:1 (weight ratio) ] to 12 copies instead of 100 copies of PVA 1
All other resin processing was performed in accordance with Example 1.

A nonwoven fabric for roofing was obtained. The results are shown in Table 1.

Comparative Example 2 Using the polyethylene terephthalate spunbond nonwoven fabric of Example 31 and without adding the copolymer of isobutylene and maleic anhydride, a conventional resin solution consisting of PVA alone was resin-processed according to Example 1. and resin adhesion 9
A 20% nonwoven fabric for roofing was obtained. The results are shown in Table 1.

As is clear from Table 1, both binders for nonwoven fabrics of the present invention have good resin impregnation properties of nonwoven fabrics, have a low resin elution rate, and are superior to conventional Pv^ binders in terms of tensile strength and tear strength. It was equally good.

On the other hand, a binder for nonwoven fabric consisting of a copolymer with a molecular weight of 190,000 had a low resin elution rate and good tensile strength and tear strength, but had poor resin impregnation.
There were problems in terms of workability. Also.

In the case of conventional PVA binders, the dissolution rate was high and the water resistance was poor.

(Effect of the invention) By using the binder for nonwoven fabric of the present invention, water resistance is high, the resin impregnation property of the nonwoven fabric is good, and the mechanical properties of the nonwoven fabric are maintained at the level of conventional PVA/< Ingu, so it is widely used. It can be used as a binder for roofing.

Patent applicant: Unitika Co., Ltd.

Claims (2)

[Claims] (1) A binder for nonwoven fabrics, characterized in that a copolymer of isobutylene and unsaturated dicarboxylic anhydride having an average molecular weight of 50,000 to 170,000 is blended with polyvinyl alcohol. (2) The binder for nonwoven fabric according to claim 1, which uses maleic anhydride as the unsaturated dicarboxylic anhydride.