JPH08325947A - Aramid short fiber for reinforcing cement - Google Patents

Abstract

PURPOSE: To obtain a fiber by collecting aramid short fibers with a specific binder, having sufficient collecting properties and dispersibility, useful for reinforcing cement, concrete, etc. CONSTITUTION: Aramid short fibers are coated with 10-50wt.% based on the weight of the fibers of a mixture of (A) a polyvinyl alcohol and (B) a water soluble polyacrylic acid ester-based copolymer as a binder. The blending ratio of the component B and the component A by weight is preferably 1.0-3.0. The pickup of the binder is readily controlled and the flexural strength of a prepared composite material is extremely improved.

Description

Detailed Description of the Invention

[0001]

This invention relates to bundled aramid staple fibers. More specifically, it relates to a short aramid fiber for cement reinforcement, which is suitable for reinforcement of cement or concrete and exhibits good bundling properties and excellent reinforcing properties.

[0002]

Conventionally, in order to improve the bending strength and impact strength of cement-based materials, asbestos, glass fiber,
Steel fibers and carbon fibers have been used. Among them, asbestos has been used for a long time, but its use is now regulated due to carcinogenic problems. Further, even if the glass fibers are alkali resistant, they are not used in a large amount because they are deteriorated by the alkali in the cement and it is difficult to maintain the reinforcing effect in the long term. Steel fibers have the problem of corrosion in the cement, which leads to cracking of the cement material. Further, even if the steel fiber is subjected to anticorrosion treatment, it cannot withstand corrosion in the long term, and the anticorrosion treatment is costly and not useful. Since carbon fiber breaks during kneading to disperse it in cement, there is a problem that it is difficult to obtain the expected reinforcing effect.

On the other hand, aramid fiber has high tensile strength, chemical resistance, and is lightweight, so that it has recently begun to be used for reinforcing cement thin plates and the like. That is, the aramid short fibers are added to the cement material, the mixture is kneaded using a ruder, and the thin plate obtained by extruding this is significantly improved in bending strength and impact resistance, and it is possible to make the thin plate thinner. Become. However, when the aramid short fibers are untreated and the bundling property is insufficient, not only is it difficult to measure the short fibers, but fiber balls are generated during kneading, and the short fibers are caught in the extruder in a predetermined amount. And the problem that sufficient dispersibility cannot be obtained easily occurs.

On the other hand, a method of applying various treating agents for the purpose of improving the sizing properties of the cement-reinforcing short fibers is described, for example, in JP-A-58-214583 and JP-A-52-8912.
It is proposed in Japanese Patent Publication No. 2 and the like. However, these treatment agents adhere to glass fibers, and even if they are applied to aramid fibers as they are, the penetration of the sizing agent into the gaps of the bundled single fiber group is still insufficient, and the treatment agent has a sufficient level. The sizing and dispersibility may not be obtained, or the dispersibility in the cement may be poor even if the sizing property is improved.
Therefore, there is a demand from the market for aramid short fibers which have sufficient sizing properties and good dispersibility in cement.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and its object is to have good converging property, easy measurement by a hopper and the like, and good dispersibility. Can exhibit excellent strengthening properties,
An object of the present invention is to provide a short aramid fiber suitable for reinforcing cement or concrete.

[0006]

The above-mentioned object is to have the following constitution: "Aramid short fibers bundled by a sizing agent, wherein the sizing agent is polyvinyl alcohol (PV
A) and a water-soluble polyacrylic acid ester-based copolymer (P
An aramid short fiber for cement reinforcement, which is composed of a mixture with A). Is achieved.

The aramid short fibers targeted by the present invention are:
As a typical example, polyparaphenylene terephthalamide, polyparaaminobenzamide, polyparaaminobenzhydrazide terephthalate, polyterephthalic acid hydrazide, polymetaphenylene isophthalamide or the like or a copolymer thereof, or a copolymer obtained by copolymerizing them with a third component. Polymers such as short fibers made of copolyparaphenylene / 3,4'oxydiphenylene / terephthalamide are used.

It is important that the sizing agent attached to the aramid short fibers is a mixture of polyvinyl alcohol (PVA) and a water-soluble polyacrylic acid ester copolymer (PA). Polyvinyl alcohol has a vinyl alcohol component of 50% in the monomer forming the polymer.
It may be mol% or more. Usually, polyvinyl alcohol is obtained by saponifying polyvinyl acetate, but the degree of saponification of polyvinyl alcohol used here may be any degree as long as the polymer is water-soluble. The stereoregularity of polyvinyl alcohol may be any of syndiotactic, isotactic, and atactic as long as the polymer is water-soluble. Further, the degree of polymerization and the degree of branching are not particularly limited as long as the water solubility condition is satisfied.

In the above water-soluble polyacrylic acid ester-based copolymer, the acrylic acid ester component in the monomers forming the polymer is 50% by weight or more, and the polymer is water-soluble. It suffices that the hydrophilic copolymerization components shown are copolymerized. Examples of the hydrophilic copolymerization component include methacrylic acid, acrylic acid, and alkali metal salts thereof, and the copolymerization amount is 10 when the hydrophilic copolymerization component is sodium (meth) acrylate.
It is about 20% by weight. The alcohol component of the above-mentioned acrylic ester may be any one as long as the polymer exhibits water solubility, and two or more alcohol components may be used in combination.

In the present invention, the mixing weight ratio of the polyvinyl alcohol in the sizing agent and the water-soluble polyacrylic acid ester-based copolymer is (PA weight) / (PVA weight) 1.0 to 3 It is preferably in the range of 0.0.
If this mixing weight ratio is less than 1.0, the proportion of the water-soluble polyacrylic acid ester-based copolymer that contributes to the improvement of the impregnation between single fibers due to the lowering of the viscosity of the sizing agent decreases, and the following problems occur. It tends to occur. That is, if the concentration of the sizing agent treatment liquid (hereinafter sometimes referred to as a mixture treatment liquid) is adjusted to control the amount of the sizing agent attached in order to obtain sufficient sizing properties, the viscosity of the mixture treatment liquid becomes too high. Problems such as gumming up on the roller surface and the like tend to occur during the treatment process, making it difficult to perform treatment continuously for a long time. On the other hand, if it exceeds 3.0, although good sizing properties are obtained, the polyvinyl alcohol component in the sizing agent, which has a particularly high affinity for water and a high solubility, becomes too small, so that it is formed between single fibers. The degradability (solubility in water) of the coating film due to water is reduced, and the dispersibility of the single fibers when kneading with cement or the like tends to be insufficient.

Needless to say, the sizing agent of the present invention may contain other components in addition to the above-mentioned two components within the range not impairing the object of the present invention.

Next, the amount of the sizing agent attached is 10 to 50% by weight, preferably 15 to 4% by weight based on the weight of the fiber.
It is desirable that the content is 0% by weight, more preferably 20 to 30% by weight. When the adhesion amount of the sizing agent is less than 10% by weight, the sizing property tends to be insufficient, which makes it difficult to handle the short fibers in the production stage of the fiber-reinforced cement,
When kneading with cement, fiber balls are easily generated. On the other hand, when it exceeds 50% by weight, although sufficient sizing properties are obtained, the dispersion of the fibers during the kneading of cement is reduced, and the sizing fibers are difficult to open into single fibers, which is effective. The fiber reinforcing effect cannot be obtained. Further, even in the treatment step of applying the sizing agent, gum up of the sizing agent or the like occurs in the roller portion or the like,
The workability is likely to be extremely poor.

Next, the number of single fibers of the aramid short fibers bundled with the sizing agent is preferably at least 100 or more. When the number of the short fibers is less than 100, workability in the treatment agent applying step and the cutting step during the production of the short fibers is deteriorated, and the bulk ratio of the short fibers after the cutting is increased, resulting in a large volume. Therefore, it is disadvantageous at the time of packing and transportation, and when kneading with cement by using an extruder, the measuring accuracy and the biting property at the time of supply are deteriorated, and fiber balls are easily generated. On the other hand, the number of single fibers is 2
When the number of fibers is more than 0000, the handling property is good when considering the packaging and transportation of short fibers, but it takes a long time to disperse when kneading into cement, and the dispersibility is poor. It tends to be insufficient. However, the upper limit is not particularly limited because it can be used depending on the application.

The method for adhering the sizing agent of the present invention to the aramid short fibers is not particularly limited, and a conventionally known method such as a coating method or a dipping method may be adopted using a treatment liquid containing the sizing agent. Good. Of these, the most simple and efficient method is to immerse the aramid fiber in the treatment liquid, squeeze it with a nip roller or the like as necessary, adjust the pickup amount of the mixed treatment liquid, and then dry and cure. Further, the drying condition at this time is generally a heat treatment at a temperature of 105 to 180 ° C. for about 0.3 to 30 minutes,
Considering equipment and efficiency, relatively low temperature 105-130 ℃
Heat treatment for about 0.3 to 15 minutes, then 130 to 18
It is preferable to perform heat treatment at a relatively high temperature of 0 ° C. for about 0.3 to 15 minutes.

[0015]

In the past, polyvinyl alcohol has been
It is widely known as a sizing agent for paper and a sizing agent for glass fibers. However, even if aramid fibers are bundled with this polyvinyl alcohol, a certain degree of bundling property is obtained,
Although the dispersibility in cement is also improved, there is a problem that the amount of the sizing agent attached cannot be increased as desired. That is, even if an attempt is made to increase the concentration of the sizing agent to increase the adhesion amount, the viscosity of the treatment liquid increases, so that gum-up occurs on the rollers of the treatment machine or the like and stable treatment cannot be performed. Further, since the treatment liquid is hardly impregnated into the single fiber gap, sufficient bundling property cannot be obtained. On the other hand, the aramid short fibers of the present invention are provided with a sizing agent consisting of a mixture of polyvinyl alcohol and a water-soluble polyacrylic acid ester-based copolymer, and the viscosity of the treatment liquid containing the sizing agent is Since the copolymer is used in combination, it can be easily lowered. Therefore, by adjusting this, it becomes possible to easily control the adhesion amount of the sizing agent, and not only sufficient sizing property can be obtained, but also the gap between the appropriately bundled single fibers is impregnated with the treatment liquid. Therefore, it is possible to obtain an aramid fiber suitable for cement reinforcement, which has good sizing property and dispersibility. Therefore, when the aramid short fibers of the present invention are mixed with cement and kneaded,
The dispersed state of the fibers is extremely good, and the bending strength of the obtained composite material is remarkably improved.

[0016]

The present invention will be described in detail with reference to the following examples. The measuring methods used in the examples are as follows. <Calculation of the amount of sizing agent attached> The fiber weight before and after the treatment is measured,
The attached amount of the sizing agent was calculated from the following calculation formula. The weight was measured after the sample to be measured was sufficiently dried. Adhesion amount (%) of sizing agent = [(weight of fiber after treatment with mixed treatment liquid)-(weight of fiber before treatment)] / (weight of fiber before treatment) × 100

<Preparation of Bending Strength Measurement Specimen> Early Strength Portland Cement 2348g, Methylcellulose 23.5g
g, treated aramid short fibers 55.6 g, and water 986 g were put into an omni mixer (model: OM-10-E, capacity: 10 liters, manufactured by GARBRO), and the rotation speed was 400 rp.
kneading for 5 minutes. And a dedicated formwork (4x4x1
(6 cm), the cement composite material after kneading was added, and the mixture was cured at room temperature for 1 month, and this was used as a bending strength test piece.

<Bundling property> When aramid short fibers are weighed and added to cement and kneaded and extruded using a ruder, no generation of fiber balls is observed (○), fiber balls are generated. Was defined as (x).

<Bending Strength Measurement> Specimen (4 × 4 × 16c
It carried out by the 3-point bending of m). That is, a 10 ton tensile / compression tester (UNIVERSAL TESTING I
NSTRUMENT MODEL UTM-10t, TO
YO BALDWWIN CO, LTD)
Compress the center of the fulcrum distance 10 cm at 2 mm / min,
Bending strength was determined from the highest point of stress.

<Evaluation of dispersibility> About 100 g of cement before curing was randomly sampled for bending strength measurement, which was prepared by kneading treated aramid short fibers, and was made into a flat plate having a thickness of about 1 mm. After the spreading, the short fibers are placed on a mesh (100 mesh) wire mesh that does not fall off, a water shower is applied to remove the cement, and the fibers remaining on the wire mesh are visually judged. When about 70% or more is dispersed in the single fiber state, it is ○, when it is dispersed in the single fiber state only in the range of 40 to 70%, it is Δ, and it is dispersed in the single fiber state only less than 40%. When there was not, it was compared and judged as x.

<Evaluation Method of Workability> Ten aramid fibers were used.
The degree of gumming (amount of gum-up) of the mixed treatment agent (bunching agent) coating adhered to the surface of the nip roller of the treatment machine after 2400 m treatment at a speed of m / min was judged. That is,
When the amount of adhesion is small and continuous processing is possible, it is ○, when it can be continuously processed by simply cleaning the nip roller surface, it is △, and the sizing agent adheres to 50% or more of the nip roller surface. When it was impossible to continue the treatment unless it was thoroughly cleaned, the result was compared and judged as x.

[Examples 1 to 6] 1500 denier / 10
After performing the following treatment using 00 filament polyparaphenylene-3,4'-diphenylether-terephthalamide fiber (Technora, manufactured by Teijin Ltd.), 6 m
An aramid short fiber for cement reinforcement was obtained by cutting into m.

In Example 1, a treatment liquid containing a mixture of polyvinyl alcohol and a water-soluble polyacrylic acid ester-based copolymer was prepared as follows. That is,
100 g of Gohsenol GL-05 (polyvinyl alcohol, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was added to about 200 g of water (30
(Below ℃) while stirring, and well dispersed, then 9
Hold at 0 ° C for 30 minutes to completely dissolve. Then, 625 g of PLASIZE T-780 (24% by weight acrylic acid solution, manufactured by Kyouka Chemical Industry Co., Ltd.) is added to the solution, and further water is added so that the total weight becomes 1000 g to obtain a mixed treatment liquid. As a result, the concentration of polyvinyl alcohol in the mixed treatment agent was 10% by weight, and the concentration of the acrylic acid ester copolymer was 15% by weight. Therefore, the total concentration of the sizing agent in the treatment liquid is 25% by weight. The treatment of aramid fibers was performed by immersing the aramid fibers in a mixed treatment liquid containing the polyvinyl alcohol and polyacrylic acid ester-based copolymer, and then squeezing lightly with a pair of nip rollers to obtain a predetermined amount of mixed treatment liquid pickup. Then, at 105 ℃ 2
It was dried for 1 minute and then cured for 1 minute. This time,
The amount of the sizing agent (mixing treatment agent) attached to the fiber surface was 26.8% by weight. The workability during processing was good (◯) as shown in Table 1. The yarn treated as described above was cut into 6 mm, and was kneaded with cement under the same conditions as in "Creating a flexural strength measurement specimen" to prepare a flexural strength test specimen, and after curing, bending The strength was evaluated. The results are shown in Tables 1 and 2. In addition, in order to evaluate the dispersibility of the single fibers, the cement / aramid single fiber mixed paste was taken out immediately after kneading and evaluated in the same manner as in the "Evaluation of dispersibility". there were. In Examples 2 to 6, PA / PV was used.
Processing was performed in the same manner as in Example 1 except that the mixing ratio of A was changed (the total concentration of the treatment liquid was 25% by weight and was not changed), and the workability, dispersibility, and bending strength were similarly evaluated. Table 1 shows the results.

Comparative Examples 1 and 2 In Comparative Examples 1 and 2, PA or PVA alone (total weight concentration of 2 was used as a sizing agent, respectively.
5% by weight), and the same treatment as in Example 1
The workability, dispersibility, and bending strength were evaluated. Table 1 shows the results.

From these results, it is necessary to use PA and PVA together in order to effectively reinforce the cement.
In the aramid monofilament treated with A or PVA alone,
It is clear that there is a problem with the reinforcing effect or workability.

[Examples 7 to 11] In Examples 7 to 11,
The treatment liquid was prepared in the same manner as in Example 1 except that the PA / PVA value was 1.5, and the total concentration of the mixed treatment agents was 15, 18, 20, 28, and 30% by weight, respectively. The same treatment as in Example 1 was performed to evaluate workability, dispersibility, and bending strength. The results are shown in Table 2.

[Examples 12 and 13] 200 denier / 1
The same procedure as in Example 1 was repeated except that 33 filaments or 1000 denier / 667 filaments of polyparaphenylene-3,4'diphenylether-terephthalamide fiber (Technora, manufactured by Teijin Ltd.) was used. , 667 bundled short fibers were obtained, and the results of evaluation of these in the same manner as in Example 1 are also shown in Table 2.

[0028]

[Table 1]

[0029]

[Table 2]

Claims (4)

[Claims] 1. An aramid short fiber bundled by a sizing agent, wherein the sizing agent is polyvinyl alcohol (PV
A) and a water-soluble polyacrylic acid ester-based copolymer (P
An aramid short fiber for cement reinforcement, which is composed of a mixture with A). 2. A mixing weight ratio (PA / PV) of polyvinyl alcohol and a water-soluble polyacrylic acid ester-based copolymer.
The aramid short fiber for cement reinforcement according to claim 1, wherein A) is 1.0 to 3.0. 3. The aramid short fiber for cement reinforcement according to claim 1, wherein the amount of the sizing agent attached is 10 to 50% by weight based on the weight of the fiber. 4. The aramid short fiber for cement reinforcement according to claim 1, wherein the number of bundles of the aramid single fiber is 100 or more.