JPS585284B2 - Manufacturing method of fibrous binder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a fibrous binder having an excellent wet paper strength enhancing effect.

As a fibrous binder, polyvinyl alcohol (hereinafter referred to as PVA) fibers are known, but although these fibers have a great adhesive effect, they have low wet paper strength, and conventionally, as a solution to this problem, paper-made paper has not been used. Water resistance is merely imparted through secondary processing using aldehydes.

In addition, as another means for imparting water resistance, paper strength enhancers such as urea-formalin resin and melamine-formalin resin have been added to improve wet paper strength.

However, paper treated with these methods has a hard texture and is not suitable for household thin paper such as tissue paper, and it also contains formalin, which has a negative effect on the human body. Its use is also avoided for hygiene reasons.

Therefore, the texture of the paper is soft, it does not contain formalin which has a negative impact on the human body from a sanitary standpoint, and even a small amount of addition can exert a sufficient effect of increasing paper strength, and the yield during mixing is also good. There is a strong need for a fibrous binder as a wet paper strength enhancer with good workability.

A method for producing a fibrous binder similar to the present invention was disclosed in Japanese Patent Application Laid-Open No. 53
-106804, the manufacturing method is a method of forming fibers from a PVA solution containing a heat-reactive water-soluble urethane, and also prevents the reaction of the heat-reactive urethane during the fiber-forming process. In order to retain the water-soluble urethane, it is characterized by low-temperature dehydration molding.For example, in the production of fibrous solids, if the coagulation bath is only salt, coagulation is slow and it is not possible to completely prevent water-soluble urethane from flowing out. - A saturated solution of ammonium sulfate containing alcohol is used in the bath, a lower alcohol is used in the second bath, and spinning is carried out at a low temperature.

However, in order to carry out the invention industrially, lower alcohols are used, which is disadvantageous in terms of cost, equipment, and occupational safety and health.

In other words, compared to wet spinning, which uses water, expensive lower alcohols are used, so the price of lost alcohol and the cost of recovering alcohol increase the cost of fibers. Since alcohol is a dangerous substance, it requires special equipment to prevent explosions, and equipment to prevent workers from coming into contact with lower alcohol vapors from the standpoint of occupational health. have

Furthermore, the obtained fibers are insufficiently heat-treated and stretched, so they cannot help but become very brittle fibers.

In addition, the reaction between lower alcohol and heat-reactive urethane is PV
Due to its strong reactivity compared to the reaction with A, another drawback in practice is that air drying is required to remove the boiling point volatile alcohol.

Therefore, the object of the present invention is to use water-based wet spinning without using lower alcohols, without air drying, and without reacting with heat-reactive polyurethane even when subjected to moist heat treatment at high temperatures. The object of the present invention is to provide a method for producing a fibrous binder, which improves the drawbacks of the prior art.

In order to prevent the reaction of heat-reactive urethane, the prior art employs a low-temperature spinning method using a lower alcohol, but as mentioned above, there are various problems.

As a result of extensive research into methods for preventing the reaction of heat-reactive urethane due to thermal history during the fiberization process, the inventor found that the masking of heat-reactive urethane becomes stronger as the pH decreases. , the present invention has been achieved.

That is, when performing wet spinning using an aqueous salt solution, if the pH of the aqueous salt solution is adjusted to 3 to 7, spinning at a high temperature,
Even if a moist heat treatment is performed, reaction of the heat-reactive urethane is prevented and the intended purpose is achieved.

Furthermore, since high-temperature spinning is possible, coagulation is quick, there is no outflow of the urethane aqueous dispersion, and the spinning speed can be increased.

Of course, since the composition is an aqueous dispersion, the dispersed heat-reactive urethane has the property of coagulating and precipitating through salts, so the urethane does not flow into the coagulation liquid containing salts and can be spun and formed at low temperatures. be.

If the pH of the aqueous salt solution is lower than 3, there is no problem in terms of the reactivity of the heat-reactive urethane, but the acid content brought into the fiber threads may cause decomposition and coloring of the fibers if left for a long time. Therefore, it is necessary to remove the acid content.

However, when the pH drops to below 3, it is extremely difficult to remove the acid content only by washing with water, and neutralization with an alkali such as soda carbonate is necessary, but alkali tends to accelerate the reaction of heat-reactive urethane. Therefore, it is necessary to avoid the use of alkali as much as possible, and it is not preferable to lower the pH to 3 or less.

If the pH is above 7, as mentioned above, the reaction of the heat-reactive urethane is promoted, so that PVA becomes insolubilized during the fiberization process, and the binder effect is extremely reduced, which is undesirable.

In the spinning method of the present invention, fibers may be formed by coagulation and wet heat stretching in one bath of a pH-adjusted salt aqueous solution, or fibers may be formed in two baths, a coagulation bath and a wet heat bath. good.

When carrying out two baths, the salts in the coagulation bath and the moist heat bath may be different, but from an industrial perspective it is desirable to use the same salts.

The pH and temperature of the coagulation bath and moist heat bath may be changed as necessary.

For coagulation and wet heat stretching, a stretching ratio of 1.5 times or more is desirable based on the spinning nozzle discharge linear speed.

Fibers made into fibers without wet-heat stretching as in the present invention are extremely sticky, so they are not easily dispersed in paper stock as a fibrous binder and are mixed with other paper stock fibers.
When paper is made, the wet paper has extremely poor texture, making it impossible to produce high-quality paper.

The heat-reactive urethane used in the present invention is an aqueous dispersion of a regenerated free isocyanate of a urethane prepolymer.
-8060, JP-A-53-126058, and the like.

Isocyanate regenerants are masked compounds that can regenerate -NCO groups, such as phenol, ε-caprolactam, diethyl malonate, acetoacetate, acetone oxime, acetylacetone, acidic sodium sulfite, etc. It is a compound in which the group is masked, and the -NCO group is temporarily protected, and if necessary, it can be regenerated by heating and used for reaction.

The masked compound used in the present invention is preferably one that provides a masked isocyanate whose temperature required to regenerate the masked isocyanate group is generally 130°C or less, preferably 50 to 100°C.

The PVA used in the present invention has an average degree of polymerization of 700 to
2500, and those containing 1.0 mol % or less of residual acetic acid groups are suitable, but the present invention is not limited to this range.

The above-mentioned mixture of heat-reactive urethane and PVA has a weight ratio of PVA/heat-reactive urethane of 8.
A range of 5/15 to 40/60 is desirable.

That is, if the PVA content exceeds 85/15, the water resistance of PVA will be significantly reduced, and a good wet paper strength enhancement effect will not be obtained.

Furthermore, if the PVA is less than 40/60, it is difficult to form fibers, and although the water resistance of PVA is good, the binder effect is significantly reduced, so it is necessary to use a large amount of fiber, which is not economical.

As the salts used in the present invention, salts used in coagulation baths for PVA fibers such as sodium sulfate, ammonium sulfate, and zinc sulfate can be used.

The pH of an aqueous solution of these salts can be adjusted using an inorganic acid such as hydrochloric acid or sulfuric acid, or an organic acid such as acetic acid or formic acid.

The features of the present invention will be described below using experimental examples.

A spinning stock solution prepared by mixing a heat-reactive urethane aqueous dispersion (masking agent is sodium acid sulfite) and a PVA aqueous solution so that the weight ratio of PVA/heat-reactive urethane was 75/25 was mixed at a temperature of 45°C and a pH of 6.0. The fibers were wet-spun in a coagulation bath of a saturated aqueous solution of sodium sulfate, and then passed through a wet heat bath of a saturated aqueous solution of sodium sulfate at different pH and temperature to perform wet heat stretching.

The fibers thus obtained were washed with water, air-dried, vacuum-dried, and tested for solubility in 80°C hot water.

The results are shown in Table 1. Table 1 shows that when the pH of the bath becomes alkaline, the solubility in hot water is extremely reduced.

The component dissolved in hot water is PVA, and from the mechanism of the binder effect of PVA, if the solubility in hot water is reduced, the binder effect is significantly reduced and the value as a binder is low.

The reason why the solubility is decreased is that the heat-reactive urethane reacts with PVA during the fiberization process, and the PVA becomes insolubilized.

As the temperature rises, the solubility decreases, but by lowering the pH of the bath, the decrease in PVA solubility due to the rise in temperature is clearly small, and the reaction prevention effect of heat-reactive urethane is recognized. It will be done.

Therefore, by appropriately combining the pH and temperature of the bath,
A fibrous binder with good binder effect that maintains the reaction of heat-reactive urethane as it is can be obtained.

The reason why the solubility in hot water is not 100% is because it contains 25% by weight of insoluble urethane.

If the solubility of the PVA component in the fiber is 90% or more, a good binder effect can be obtained.

The prepared spinning stock solution was wet-spun in a coagulation bath of a saturated aqueous sodium sulfate solution at a temperature of 45°C and a pH of 6.0, and then
, wet heat stretching was performed at a temperature of 70°C.

The threads collected in each step were lightly washed with water, and the state of stickiness of the threads was observed.

The results are shown in Table 2. From Table 2, fibers that are not subjected to wet heat stretching (No. 1) and fibers that are subjected to wet heat stretching but whose draw ratio is low (No.

In 2), adhesion is observed and it is not a practical fiber.

However, the fibers (No. 3, 4) that were subjected to wet heat stretching at a draw ratio of about 1.5 times or more were good fibers without sticking.
It has practical value as a fibrous binder.

The present invention will be explained below with reference to Examples.

Example 1 100 parts of polypropylene glycol (molecular weight 2000) and 17.5 parts of 4,4-diphenylmethane diisocyanate were added.
Add 4 parts and keep at 130°C for 10 minutes then 40°C
Cool to

NC010H=2.02, free isocyanate group 3.58% by weight, actual value 3.
42% by weight A 7:3 mixed solvent of isopropyl alcohol and methyl alcohol was added to 100 parts of the obtained urethane prepolymer.
0 parts, 35% by weight acidic sodium sulfite aqueous solution 34.6
After reacting at 40° C. for 3 hours, the mixture was left at room temperature overnight and diluted with water to a urethane concentration of 25% by weight to obtain a heat-reactive urethane aqueous dispersion.

Completely saponified PVA with a degree of polymerization of 1500 dissolved in water at a concentration of 1
760 parts of the 6% by weight solution and 160 parts of the above 25% by weight heat-reactive urethane aqueous dispersion were mixed at a temperature of 40°C, and the resulting dispersion was stirred well and used as a spinning stock solution at a pH of 4.5 and a temperature of 80°C. The fibers were spun into a bath of a saturated aqueous sodium sulfate solution, stretched three times in the same bath, lightly washed with water, dehydrated with a squeezing roller, and rolled up.

The solubility of the obtained fiber in 80°C hot water is 68% (PVA
It was a good fiber with no adhesion (calculated 91%).

Example 2 A 30% by weight heat-reactive urethane aqueous dispersion was prepared by the method described in Example 2 of JP-A-53-126058.

Polymerization degree 1650 Completely saponified PVA dissolved in water Concentration 1
800 parts of 4% by weight and 267 parts of the 30% by weight heat-reactive urethane aqueous dispersion prepared above were mixed at a temperature of 40°C and stirred well. The resulting dispersion was used as a spinning dope and had a pH of 3.7.
, wet spinning using a saturated mirabilite bath at a temperature of 45°C, followed by stretching 2.5 times in a saturated mirabilite bath at a pH of 3.7 and a temperature of 90°C, washing with water, and dewatering with a squeezing roller to obtain a fiber. I flipped it up.

The solubility of the obtained fiber in 80°C hot water was 54% (PVA
It was a good fiber with no adhesion (calculated as 92%).

Example 3 Poly(ethylene adipate) glycol (OH.

Dissolve 202.5 parts of V=55.8) in 101.7 parts of methyl ethyl ketone, put it in a flask, and add 2.4 parts to it.
- adding 34.8 parts of an 80:20 mixture of tolylene diisocyanate and 2,6-tolylene diisocyanate;
The reaction was carried out at 80° C. for 3 hours to obtain a urethane prepolymer solution containing 2.45% of free isocyanate groups.

5 parts of a 7:3 mixed solvent of isopropyl alcohol and methyl alcohol was added to 100 parts of the obtained urethane prepolymer.
0 parts, 30% by weight acidic sodium sulfite aqueous solution 27.7
After adding 1 part of water and reacting at 40°C for 2 hours, add 1 part of water.
Add 30 parts and distill off the organic solvent under reduced pressure to give 30% by weight.
A heat-reactive urethane water dispersion was prepared.

Polymerization degree 1200 completely saponified PVA dissolved in water at a concentration of 1
Mixing 800 parts of the 4% by weight solution and 171 parts of the 30% by weight heat-reactive urethane aqueous dispersion prepared above at a temperature of 40°C,
The dispersion obtained by stirring well was used as a spinning stock solution, and the pH was adjusted to 4.
, 2. The fibers were spun into a bath of a saturated aqueous sodium sulfate solution at a temperature of 70°C, and simultaneously stretched to 2.5 times in the same bath, and the liquid was removed using a squeezing roller to wind up the fibers.

The solubility of the obtained fiber in 80°C hot water is 65% (PVA
(calculated 95%), and the fibers were of good quality with no sticking.

Example 4 1 mol of polyoxypropylene triol having an equivalent weight of 1026 was mixed with 3 mol of p-phenylene diisocyanate, and reacted at 80°C for 2 hours.

After cooling to 40°C, 1.5 mol of methyl ethyl ketone oxime was added, and the mixture was reacted at 60°C for 1 hour to obtain a prepolymer with masked isocyanate groups.

Mix 40 parts of toluene with 100 parts of this prepolymer,
Aqueous solution 10 containing 6 parts of polyoxyethylene nonylphenol ether with an added mole number of ethylene oxide of 40
6 parts were added and emulsified using a colloid mill.

The heat-reactive urethane concentration of this emulsion was 40% by weight.

Polymerization degree 1600 completely saponified PVA dissolved in water at a concentration of 1
800 parts of the 4% by weight solution and 280 parts of the 40% by weight heat-reactive urethane aqueous dispersion prepared above were mixed at a temperature of 50°C, stirred well, and the resulting dispersion was used as a spinning dope and saturated at a temperature of 45°C. Wet spinning was carried out in a coagulation bath containing an aqueous ammonium sulfate solution, followed by stretching to 1.5 times in a wet heat bath containing a saturated aqueous ammonium sulfate solution at pH 6.3 and a temperature of 70° C., dewatering was performed with a squeezing roller, and the fiber was rolled up.

The solubility of the obtained fiber in 80°C hot water was 47% (PVA
It was a good fiber with no adhesion (calculated as 94%).

Example 5 Daiichi Kogyo Seiyaku Co., Ltd. has a heat-reactive urethane water dispersion (■
Elastron E-37) 114 parts of a 28% by weight solution and 800 parts of a 16% by weight solution of fully saponified PVA with a degree of polymerization of 1600 dissolved in water are mixed at a temperature of 40°C, and the resulting dispersion is stirred well and used as a spinning dope. As, pH 5.5, temperature 8
It was spun into a bath of saturated Glauber's salt aqueous solution at 0°C, and at the same time 3
It was stretched twice, dehydrated with a squeezing roller, and the fibers were rolled up.

The solubility of the obtained fiber in 80℃ hot water is 82% (PVA
(calculated 103%), and the fibers were of good quality with no sticking.

Claims (1)

[Scope of Claims] 1. A spinning stock solution in which polyvinyl alcohol and a heat-reactive urethane aqueous dispersion are mixed is adjusted to pH 3 to 7 so that the weight ratio of polyvinyl alcohol and heat-reactive urethane is 85:15 to 40:60. A method for producing a fibrous binder characterized by wet spinning in a coagulation bath made of a prepared aqueous salt solution. 2. The method for producing a fibrous binder according to claim 1, wherein the wet-spun fibers are subjected to wet heat stretching in a bath consisting of an aqueous salt solution adjusted to pH 3 to 7.