JPS6153385B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coating of chopped glass fiber strands with a thermosetting resin such as an epoxy resin or a phenolic resin, a molding resin composition comprising a thermoplastic resin such as a thermoplastic polyester resin or a polyamide resin, and a method for producing the same.
More specifically, the chopped strands of glass fiber impregnated with the above thermosetting resin solution are dispersed in an aqueous medium, and the chopped strands are individually prepared by dispersing the chopped strands in an aqueous medium and removing the solvent. The present invention relates to a molding resin composition comprising a thermosetting resin coating, particularly a thick coating, and the above-mentioned thermoplastic resin, and a method for producing the same. Glass fiber-containing thermoplastic resins are widely used as various molding materials, such as molding materials for electrical parts and impact-resistant materials. Additionally, as automobiles become lighter in weight, they are also attracting attention as an alternative material to metals. Conventionally, these glass fiber-containing thermoplastic resin molding materials are generally produced by heating and melting mixing chopped glass fiber strands and thermoplastic resin using an extruder, and then forming the mixture into a form that can be injection molded, that is, into pellets. It was getting worse. However, in the above mixing process, the glass fiber chopped strands are opened before the mixing process, resulting in poor conveyance and metering properties, or the glass fibers are not uniformly dispersed in the resin during the extruder mixing process. As a result, the glass fibers are cut short, reducing the performance of the glass fiber-containing thermoplastic resin molded product. In order to solve this problem, in recent years, glass fiber chopped strands have been coated thickly with thermoplastic resin in advance. It has been proposed that the strength of molded products can be improved without causing poor dispersion. A typical method is coating with styrene resin. That is, styrenic monomers are polymerized in an aqueous medium containing a suspension stabilizer in the presence of chopped glass fiber strands using a specific reaction vessel under special mixing conditions. This is a method in which the strands are heavily coated with styrene resin. According to this method, it is possible to obtain a pellet-rich coating of chopped strands of styrene resin, and it has achieved some success as a glass fiber-containing molding material, but since this method uses a polymerization method, It takes 2 to 8 hours, and this has a significant negative impact on productivity and cost. Furthermore, since the thick coating mainly consists of styrene type resin, if a thermoplastic resin other than styrene type resin such as nylon, polybutylene terephthalate, polyethylene terephthalate, polycarbonate, etc. is applied as a matrix to this thick coating. Although it can satisfy the dispersibility of glass fibers in direct injection molding, it has poor adhesion at the interface between glass fibers and matrix resin, as well as poor compatibility between resin and matrix in dense coatings. Due to the poor quality, the physical properties deteriorate, and the glass fiber cannot fully exert its effect as a reinforcing agent. The first object of the present invention is to provide a coating by a simpler method with excellent productivity in manufacturing such a dense coating. A second object of the present invention is to provide a thick coating that enables direct injection molding and improves its performance when applied to various thermoplastic resins. The method for thickly coating chopped glass fiber strands of the present invention which achieves the above object is to immerse chopped glass fiber strands in various thermosetting resins, such as epoxy resin solution or phenolic resin, to impregnate the chopped strands. Dispersing the chopped strands and removing the solvent from the impregnated resin solution in an aqueous medium, and after removing the solvent, separating the chopped strands coated with a thermosetting resin from the aqueous medium and drying them. It is characterized by In the above-mentioned invention, the chopped strands of glass fibers (hereinafter simply referred to as chopped strands) are twisted from a bushing, coated with a binding agent, and then bundled and wound up. It is formed by cutting the strands. As the sizing agent, a commonly used sizing agent for glass fibers consisting of a film former, a surface treatment agent, and a lubricant can be used. Chopped strands have no critical meaning, but they usually contain fibers with a diameter of 7 to 23μ.
Those containing 100 to 4000 pieces and having a cut length of 1.5 to 25 mm are used. A case where an epoxy resin is used as the thermosetting resin will be described below. The chopped strands are impregnated with an epoxy resin solution. Impregnation can be accomplished by simply dipping the chopped strands into a resin solution. At this time, the strands are usually soaked for about 10 minutes to be sufficiently impregnated with the resin solution. The amount of impregnation is determined by considering the viscosity of the resin solution and the amount of resin coating desired for the final product, but generally the non-volatile content of the resin is about 5 to 50 parts by weight per 100 parts by weight of the chopped strand. are selected as such. The viscosity and concentration of the resin solution at this time vary depending on the desired molecular weight of the epoxy resin, but preferably the epoxy resin solution viscosity is 10 centipoise to 10 centipoise.
The solution concentration may be adjusted to within 3000 centipoise. If the resin non-volatile content is less than 5% by weight, the glass fibers will not be coated uniformly and poor dispersion will occur in the molded product, which is not preferable. Moreover, if it is more than 50% by weight, the compatibility with the thermoplastic resin matrix is impaired, which is unfavorable in terms of performance. A preferred amount of impregnation is about 10 to 30 parts by weight of epoxy resin non-volatile content per 100 parts by weight of chopped strands. Further, it is more preferable to perform vacuum defoaming as an impregnating means when dipping the chopped strands. The epoxy resin to be coated on the chopped strands of the present invention may be any compound containing two or more epoxy groups in the molecule, but preferably one that is solid at room temperature. This is preferably non-stick since the epoxy resin-coated chopped strands are separated from the aqueous medium and then dried with hot air (40°C to 60°C), and dry blended with the thermoplastic resin matrix. It is also preferable from the point of view of ease of handling. Preferred epoxy resins have the following structural formula. The solvent for preparing the epoxy resin solution is preferably one that can be removed into an aqueous medium, such as acetone, diacetone alcohol, tetrahydrofuran, methyl ethyl ketone, and the like. After the chopped strands impregnated with the epoxy resin solution have been separated from the resin solution, for example by screening, they are introduced into an aqueous medium with stirring. Alternatively, following the separation, the resin-impregnated chopped strands may be squeezed if necessary to adjust the content. Surprisingly, by adding the resin-impregnated chopped strands to an aqueous medium and stirring them, the chopped strands are uniformly dispersed individually and impregnated with resin in the aqueous medium. By this addition and dispersion, the impregnating resin solution is desolvented into the aqueous medium. In the above-mentioned dispersion step, the ratio of the aqueous medium to the impregnated chopped strands must not be so small as to inhibit the dispersion of the chopped strands, but there is no particular restriction as long as it is higher than that. However, it is not preferable from a practical point of view to use too much aqueous medium because it leads to an increase in the size of the apparatus. The aqueous medium is generally used in a weight ratio of about 10:1 to 10:3 to the impregnated chopped strand. Stirring during dispersion does not require strong stirring;
Generally, stirring at about 100 to 300 rpm is sufficient. However, the strength of stirring depends on the amount of aqueous medium, the dispersion concentration, etc., and therefore it is better to adjust it to an appropriate value while actually observing the dispersion state. Due to this stirring, a part of the resin solution impregnated into the chopped strands may transfer to the dispersion medium and the system may become cloudy. Does not substantially affect the coating. On the other hand, the resin that has migrated in this way is adsorbed to the chopped strands when the system is heated, and
It has been observed that the dispersion medium becomes clear. The temperature of the dispersion medium when dispersing the impregnated chopped strands is not particularly limited, but lower temperatures are generally preferred because they provide better conditions. And normally a sufficiently good dispersion is achieved at a temperature of about 10-30°C. Dispersion may be carried out by continuing stirring at such a temperature for a sufficient time to remove the solvent, but it is preferable to remove the solvent by raising the temperature after adding the impregnated chopped strands. is good.
Although the temperature increase limit depends on the type of solvent used to dissolve the epoxy resin, it is preferable to increase the temperature to 40 to 70°C. This temperature increase promotes desolvation and causes the resin transferred to the aqueous medium as described above to be adsorbed onto the chopped strands. However, if the amount of epoxy resin coated is large, the resin-impregnated chopped strands may harden into lumps, making it impossible to form a clean resin coat. In such a case, by adding an effective amount of a dispersant to the aqueous medium in advance, agglomeration can be prevented and a uniform dispersion state can be maintained. Dispersants can be used not only in this case but also for the purpose of promoting initial dispersion. As the dispersant, known ones such as water-soluble polymers such as polyvinyl alcohol can be used. The amount of dispersant is sufficient within the conventional range and is usually added in an amount of about 0.1 to 10% by weight relative to the aqueous medium. The dispersion time is the time during which substantially all of the solvent is removed from the impregnated resin solution into the aqueous medium, and usually about 30 to 90 minutes is sufficient. After dispersion and solvent removal are completed, if the temperature of the dispersion system is raised in the dispersion process, preferably, after cooling to room temperature, the chopped strands individually coated with the epoxy resin are separated from the dispersion system. . Separation can be carried out in a conventional manner, for example by screening. The separated epoxy resin coated chopped strands can be dried by any method, such as hot air drying. Drying is 40
A temperature of ~60°C is optimal. Thus, according to the invention, simple equipment and impregnation,
Chopped glass fiber strands can be coated with epoxy resin by simple operations of dispersion, separation, and drying, and in an extremely short time. According to the above-mentioned coating method, it is possible to obtain a pellet-like glass fiber base material that is uniformly filled and coated with an epoxy resin, and is particularly densely coated, without causing the glass fibers to become fluffed, which can cause molding troubles. I can do it. The epoxy resin-coated chopped strands according to the invention can be directly injection molded in the form of a dry blend with glass fiber-free thermoplastic resin pellets, and the glass fibers are evenly distributed in the molded article and A molded article with extremely excellent properties can be obtained. The amount of dry blend is
The glass fiber content in the molded article is selected in the range of 5 to 60% by weight. In addition, examples of thermoplastic resins include polypropylene, which is commonly used for injection molding.
polyethylene, polystyrene, poly(styrene)
acrylonitrile) copolymer, nylon, polybutylene terephthalate, polyethylene terephthalate, polycarbonate, polyacetal, polyphenylene oxide, etc. Next, the present invention will be further explained with reference to Examples.
However, these examples are merely illustrative and should not be construed as limiting the invention. Example 1 300 parts by weight of chopped strands of glass fibers with a cut length of 3 mm consisting of 800 glass fibers with a diameter of 13 μm treated with a sizing agent mainly composed of polyurethane emulsion were dissolved in 75 parts by weight of methyl ethyl ketone. The sample was immersed in a solution of 75 parts by weight of a bisphenol type epoxy resin having an epoxy equivalent of 940. 3000 parts by weight containing 3 parts by weight of polyvinyl alcohol prepared in advance in 5 tanks equipped with this stirrer and solvent recovery device at a temperature of 20℃
The mixture was poured into an aqueous medium, and the temperature was raised to 70°C while stirring.
During this heating process, the impregnated chopped strands exhibited a completely uniform dispersion state. The time required during this time was 30 minutes. After this dispersion was allowed to cool to room temperature, the chopped strands coated with the epoxy resin were separated by filtration and dried with hot air at 40°C.
All of the resulting resin-coated chopped strands were coated with epoxy resin uniformly on each chopped strand, even to the inside, and the amount of resin was 20% by weight, which matched the initial charge amount. It was hot. The epoxy resin-coated chopped strand and polybutylene terephthalate (Toray 1401) were dry blended. The glass content in this dry blend was set to 30% by weight, test pieces were prepared by injection molding, and various physical properties were measured. As measurement items, Izot impact value and tensile strength were measured (JIS K6911). The results are shown in Table 1. Comparative Example 1 (Comparison with Example 1) 300 parts by weight of chopped strands of glass fibers each having a cut length of 3 mm and consisting of 800 glass fibers with a diameter of 13 μm treated with a sizing agent mainly composed of polyurethane emulsion. The mixture was mixed with 700 parts of polybutylene terephthalate (Toray 1401), pelletized using an ordinary extruder, and then injection molded to prepare test pieces and their physical properties were measured. The results are shown in Table 1. Example 2 300 parts by weight of chopped glass fibers having the same morphology as in Example 1 treated with a sizing agent mainly composed of an epoxy resin emulsion were dissolved in 34 parts by weight of methyl ethyl ketone and having an epoxy equivalent of about 450. Bisphenol type epoxy resin 34
Part by weight solution was immersed and impregnated. This was subjected to the same operation as in Example 1 in an aqueous medium containing no polyvinyl alcohol to obtain an epoxy resin-coated chopped strand. In the obtained epoxy resin coating, each chopped strand was uniformly coated to the inside, and the amount of resin was 10% by weight. Example 1 This resin-coated chopped strand
Molding was carried out using the same composition. Table 1 shows the results of measuring the physical properties of the obtained test piece. Comparative Example 2 (Comparison with Example 2) Glass fiber chopped strands having the same morphology as in Comparative Example 1 and treated with a sizing agent mainly composed of epoxy resin emulsion were subjected to the same operation as in Comparative Example 1. Therefore, test pieces were prepared and various physical properties were measured. The results are shown in Table 1.

[Table] Example 3 300 parts by weight of the same chopped glass fiber strand as in Example 1 was coated with epoxy resin in a solution of 75 parts by weight of a bisphenol type epoxy resin having an epoxy equivalent of about 3200 dissolved in 75 parts by weight of methyl ethyl ketone. I created chopped strands. The coverage was 20% by weight. This epoxy resin-coated chopped strand is mixed with 6,6-nylon pellets in the form of a dry blend so that the glass fiber content is 30% by weight.
A test piece was created using an injection molding machine. The appearance of the molded product is
No poor dispersion of glass fibers was observed at all.
The physical properties are shown in Table 2. Comparative Example 3 (Comparison with Example 3) 6.6- instead of polybutylene terephthalate
Comparative Example 1 was repeated using nylon. Table 2 shows the measurement results of the physical properties of the obtained test piece.

[Table] From Tables 1 and 2, the physical properties of the molded product using the epoxy resin-coated chopped strand obtained by the method of the present invention are superior to those of the comparative example, and the extruder process commonly used It is clear that it is possible to omit this and directly apply it to the injection molding machine. Similar results were obtained when a phenolic resin was used instead of the epoxy resin as the thermosetting resin.

Claims (1)

[Scope of Claims] 1. A chopped strand of glass fiber whose surface has been treated with a sizing agent and which is further coated with 5 to 50 parts by weight of an epoxy resin or phenolic resin per 100 parts by weight of the glass fiber, and consisting of thermoplastic polyester resin or polyamide resin,
Molding resin composition. 2 After spinning and convergence, cut the chopped strands of glass fiber into a predetermined length and dip them in an epoxy resin or phenolic resin solution to coat the chopped strands with the epoxy resin or phenolic resin solution. After separating the impregnated chopped strands, this is stirred in an aqueous medium to disperse the impregnated chopped strands and remove the resin solution impregnated into the chopped strands from the aqueous medium. The chopped strands coated with the epoxy resin or phenolic resin after the solvent removal are separated from the aqueous medium and dried, and the resulting glass fibers coated with the epoxy resin or phenolic resin are separated from the aqueous medium and dried. A method for producing a molding resin composition, comprising dry blending chopped strands of the above with a thermoplastic polyester resin or a polyamide resin.