JPH0768378B2 - Fiber-reinforced thermosetting resin molding material - Google Patents

Description

The present invention relates to a fiber-reinforced thermosetting resin molding material. More specifically, it relates to a molding material that is made by mixing and impregnating pre-cut glass fiber bundles with a thermosetting resin composition such as unsaturated polyester resin or vinyl ester resin, and then applying the mixture to an injection molding machine or transfer molding machine to heat and pressurize the mixture to form a product.

BACKGROUND ART Generally, compression molded products using sheet molding compound (hereinafter abbreviated as SMC) as a molding material are
While it has high strength and rigidity, it has drawbacks in terms of surface finish and production cycle, while injection molded products using bulk molding compound (hereinafter referred to as BMC) have good surface finish and a short production cycle, but poor mechanical strength.Although injection molding using BMC has been used for a long time, it is mostly used for small molded products such as electrical parts, and is rarely used for large molded products, because of its low strength characteristics, especially impact strength.

Conventionally, BMC used in injection molding has been produced by impregnating cut glass fiber bundles with an unsaturated polyester resin composition using a kneader such as a double-arm kneader. During this production process, the glass fiber bundles are opened, bent, or damaged by the mechanical shearing force. Therefore, even when the BMC material is produced, i.e., when it is compression molded to prevent further damage to the glass fiber bundles in the BMC, it is already an SMC.
The impact strength achieved is only about half that of the conventional type.
Furthermore, during the injection or transfer molding process, which involves feeding BMC into a stuffer, forcing it into a plunger or screw, transferring it, metering it, injecting it, and flowing it into the mold before it hardens, the mechanical forces that the BMC is subjected to cause the glass fiber bundles in the BMC to open up significantly, causing even more bending and damage.As a result, the products obtained by injection or transfer molding BMC have extremely low impact strength, less than one-quarter that of compression-molded SMC products.

Therefore, in the past, in the production of BMC, efforts have been made to shorten the mixing time, for example, to optimize the mixing machine (Patent Document 1).
Although various efforts have been made to improve the glass fiber bundle strength (Japanese Patent Application Laid-Open No. 3,932,980), and to make the glass fiber bundle less susceptible to splitting and damage by examining the type of binder for the glass fiber bundle and adjusting the amount of binder attached, to make the glass fiber bundle less susceptible to breakage and tangling by shortening the glass fiber length to about 1/4 inch (Japanese Patent Application Laid-Open No. 57-41,918), and to reduce damage caused by friction between fibers by limiting the glass content in BMC to 20% by weight or less, no significant improvements have been made.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a novel fiber-reinforced thermosetting resin molding material.

Another object of the present invention is to provide a fiber-reinforced thermosetting resin molding material that has significantly improved mechanical properties, particularly impact strength, while maintaining the advantages of conventional BMC, such as excellent surface properties and productivity, and that can be used to obtain medium- and large-sized molded articles with excellent practicality.

DISCLOSURE OF THE INVENTION The above objects can be achieved by a fiber-reinforced thermosetting resin molding material which comprises a liquid thermosetting resin composition containing a styrene monomer as a crosslinking component and cut pieces of glass fiber bundles, and which is introduced into a mold using a plunger or screw mechanism for hot and pressure molding, characterized in that the glass fiber bundles have a fiber count in the range of 600 to 1,400, the amount of binder attached to the glass fiber bundles is 1.0% by weight or more, and the amount of insoluble components in the binder relative to the styrene monomer is in the range of 40 to 90% by weight, and the cut pieces of glass fiber bundles have a length of 6 to 25 mm.

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the diameter of the glass fiber single fibers forming the glass fiber bundle may be selected from the conventionally commonly used fibers having a diameter of about 8 to 13 μm depending on the application. For example, when two types of fiber diameters, 11 μm and 13 μm, are compared, the diameter of 13 μm is
The molding material using 13 μm diameter glass fibers can achieve a material strength (compression molded product strength) that is about 6% higher. However, the final molded product strength of injection or transfer molded products made from molding material containing thick glass fibers with a 13 μm diameter is lower than that of the compression molded product.
The strength level was equivalent to that of molding materials using 11 μm diameter fibers.

The length of the cut glass fiber bundle is usually 6 to 25 mm.
From the viewpoint of the strength of the resulting molded product, a length of 12 to 18 mm is optimal. Fibers longer than 25 mm are not preferred because, depending on the capacity of the molding machine, it may become difficult to smoothly measure and transfer the resulting molding material during injection or transfer molding.

Regarding the content of cut glass fiber bundles, in order to achieve practical strength for injection or transfer molded products,
It is best to have as much as possible of the glass fiber content in the molding material, at least 15% by weight. However, if it exceeds 30% by weight, the glass fibers will rub against each other and become tangled, which will actually reduce the strength of the final molded product and cause defects in the surface of the molded product. Therefore, 15 to 25% by weight is optimal.

Regarding the number of fibers in the glass fiber bundle, in molding methods such as pultrusion and filament winding, which require uniform tension to be applied to the fiber bundle during molding, fiber bundles with a high number of fibers, approximately 1,600 to 4,000, are generally used. However, in molding materials such as BMC and SMC, which contain cut pieces of randomly oriented fiber bundles, good dispersion and impregnation of the cut pieces of fiber bundles is required for the quality of the molded product, such as the surface properties and mechanical strength. Therefore, taking into account the dispersion and impregnation properties, glass fiber bundles with a number of fibers of approximately 200 to 400 have been used. For example, Japanese Patent Laid-Open No. 140,375/1978 discloses a glass roving (trade name 2) with a number of fibers of 400 as a glass fiber bundle for SMC.
It is disclosed that a 40PA549SJ (manufactured by Nitto Boseki Co., Ltd.) is used.

However, the present inventors have conducted research from the viewpoint that, in molding processes such as injection or transfer molding, which are subject to large mechanical forces throughout the entire process from supplying the molding material to curing, kneading of the thermosetting resin composition with the cut pieces of glass fiber bundles occurs even during the molding stage, and therefore, even if glass fiber bundles with a higher fiber count are used, there may be no problems with the dispersion and impregnation of the cut pieces of glass fiber bundles in the molded product. They have found that, when cut pieces of glass fiber bundles with a fiber count of 600 to 1,400, more preferably 800 to 1,000, are used, the dispersion and impregnation are good, and injection or transfer molded products with excellent impact strength and surface properties can be obtained. That is, when the fiber count exceeds 1,400, the dispersion and impregnation of the fiber bundles become insufficient, and a fiber pattern due to the difference in shrinkage rate between the resin-rich and fiber-rich areas appears on the surface of the molded product, resulting in poor surface smoothness.
If the number of fibers is less than 0, the strength of the final molded product will be poor.
While various binders have been used in the past, in the present invention, a binder is selected in which the ratio of insoluble components to styrene monomer in the binder is controlled within a certain range, and glass fiber bundles with a controlled binder adhesion amount are used, thereby obtaining a molding material with excellent molded product strength without the fiber pattern appearing on the surface of the molded product and impairing the surface quality of the molded product. The ratio of insoluble components to styrene monomer in the binder varies slightly depending on the type of binder, but the strength of the molded product obtained is higher when a binder with a higher ratio of insoluble components of styrene monomer is used. The solubility of a binder immersed in styrene monomer increases with the lapse of immersion time, but even fibers with a large change reach a certain solubility and become saturated after several hours, resulting in almost no change. On the other hand, SMC and BMC are
To improve handling, magnesium oxide,
Because the method includes a thickening step using a thickener such as magnesium hydroxide or calcium hydroxide, the viscosity increases in a relatively short time, making it difficult to impregnate the glass fiber bundles. Therefore, when mixing glass fiber bundles into a liquid thermosetting resin composition and impregnating the fiber bundles, it is preferable that the binder be dissolved to a certain level by the styrene monomer in the resin composition in a relatively short time in order to achieve sufficient impregnation and obtain a molding material with excellent surface properties and strength. If the binder dissolves excessively, the glass fiber bundles in the resulting molding material will open up into single fibers, making them susceptible to damage during the injection or transfer molding process, and preventing the production of molded products with excellent impact strength.

The amount of insoluble components relative to the styrene monomer in the binder of the glass fiber bundle in the present invention is measured based on the weight loss after immersing the glass fiber bundle in styrene monomer for 1 hour. The amount of binder attached to the glass fiber bundle is measured by the ignition loss method described below. The amount of insoluble components used should be 40 to 90% by weight, with 45 to 85% by weight being particularly desirable. If the amount of insoluble components is less than 40% by weight, the glass fiber bundle will open significantly during the manufacturing process and molding process of the molding material, making it impossible to obtain a molding material with excellent molded product strength. If the amount of insoluble components exceeds 90% by weight,
In the molding material production process, the fiber bundles are not sufficiently impregnated with the liquid thermosetting resin composition, which not only impairs the surface properties of the molded product but also results in a molding material with poor molded product strength.

The amount of binder attached to the glass fiber bundle varies depending on the type of binder used, but if it is 1.0% by weight or more, glass fiber bundles up to about 2-3% by weight, which is the maximum amount that can be attached, can be effectively used, and among them, 1.7% by weight
The above is desirable. In other words, if the binder adhesion amount is less than 1.0 wt%, problems will arise in handling the fiber bundle, such as opening the glass fibers when they are cut, and a molding material with high molded strength will not be obtained. The binder adhesion amount was measured by measuring the loss on ignition as specified in JIS R 3420.

The liquid thermosetting resin composition used in the present invention is a mixture of a radical polymerizable resin, such as an unsaturated polyester resin or a vinyl ester resin, which is liquid at room temperature and contains styrene as a crosslinkable monomer, and additives commonly used in the art, such as a filler, a thickener, a mold release agent, a curing catalyst, a colorant, a shrinkage reducing agent, an ultraviolet absorber, etc. The viscosity of the resin composition is
It is 100 to 10,000 poise, preferably 400 to 3,000 poise.

The unsaturated polyester is prepared by dissolving, in styrene monomer, an unsaturated polyester which is a polycondensation product of an acid component consisting of an α,β-unsaturated dibasic acid such as maleic anhydride or fumaric acid and/or its anhydride, and optionally a saturated polybasic acid such as phthalic anhydride, tetrahydrophthalic anhydride, tetrachlorophthalic anhydride or succinic anhydride, with a polyhydric alcohol such as ethylene glycol, diethylene glycol, propylene glycol, 1,3-butanediol or hydrogenated bisphenol A. The vinyl ester resin is prepared by dissolving, in styrene monomer, a vinyl ester obtained by esterifying, with acrylic acid or methacrylic acid, a compound having at least two epoxy groups in the molecule, such as an epoxy resin derived from bisphenol A, bisphenol F, brominated bisphenol A, phenol novolac, brominated phenol novolac, cresol novolac or the like, with epichlorohydrin and/or 2-methylepichlorohydrin, or a modified product thereof.

When the resin composition is used to form SMC or BMC by the method of the present invention, the filler may be, for example, calcium carbonate, aluminum hydroxide, alumina, silica, clay, feldspar powder,
Powdered inorganic materials such as river sand and suiishi can be used in an amount of 0 to 400 parts by weight, preferably 100 to 300 parts by weight, and most preferably 150 to 250 parts by weight, per 100 parts by weight of the resin composition.

The resin composition used in the present invention may contain, if necessary, a thickener such as magnesium oxide or magnesium hydroxide,
Other known low-profile agents such as polystyrene, silane coupling agents, mold release agents such as zinc stearate and calcium stearate, thixotropic agents, plasticizers, pigments and colorants, flame retardants and flame resistant agents, etc. may also be added.

The resin composition thus obtained is blended with a radical polymerization initiator, which is then molded under heat and pressure. Examples of the radical polymerization initiator include t-butyl peroxybenzoate, benzoyl peroxide, cumene hydroperoxide, t-butyl peracetate, and 2,5-dimethylhexyl-2,5-peroxybenzoate. The amount of the polymerization initiator blended is 0.2 to 10% by weight, preferably 0.5 to 2% by weight, based on the resin composition.

To produce the fiber-reinforced thermosetting resin molding material of the present invention using the resin composition and the cut pieces of glass fiber bundles, the cut pieces of glass fiber bundles are blended with the resin composition, and the cut pieces of glass fiber bundles are dispersed and impregnated using a conventionally known mixing method, for example, a kneading machine such as a double-arm kneader or a co-kneader, and then, if necessary, aged at 20 to 60°C, preferably 30 to 50°C, for 5 to 300 hours, preferably 10 to 100 hours.

Further, the fiber-reinforced thermosetting resin molding material according to the present invention is
As described in DE 35 15 483 A1, the thermosetting resin composition can also be produced by a method in which a liquid thermosetting resin composition is supplied to the surface of at least one rotating transport roller, the composition adhering to the surface is spread in particulate form by a spreader roller that rotates in the same direction as the transport roller at a gap therebetween, and the composition is deposited in a mixed state with reinforcing fibers that have been separately spread, and the deposit is then degassed to impregnate the deposit with the resin composition.

The spraying roller comes into contact with the transported resin composition on the surface of the transport roller at high speed, scraping the resin composition and simultaneously turning it into particles and blowing it away. For this reason, both rollers rotate in the same direction to increase the relative peripheral speed between them. In addition, to increase the peripheral speed, it is desirable that the diameter of the spraying roller is smaller than that of the transport roller. Furthermore, the transport roller sprays the resin composition supplied to the surface of the roller with
Since it is used to transport the material to the position of the spraying roller, the rotation speed is relatively low, usually 100 to 1,000 rpm.
On the other hand, since the spreading roller is used to scrape and spread the resin composition, its rotation speed is high, usually 3,000 to 10,000 rpm.
The rotation speed is preferably 5,000 to 7,000 rpm. One spreading roller per transport roller is sufficient.

The fiber-reinforced thermosetting resin molding material of the present invention can be molded by conventional methods such as injection molding, transfer molding, compression molding, and extrusion molding, but it exhibits particularly excellent effects when molded by injection molding and transfer molding.

Next, the present invention will be described in more detail with reference to examples.

The thermosetting resin used in the examples was an unsaturated polyester resin (Epolac N-21, manufactured by Nippon Shokubai Kagaku Kogyo Co., Ltd.), and the shrinkage reducing agent was Epolac AT-100.
(manufactured by Nippon Catalyst Chemical Industry Co., Ltd.). As the glass fiber bundle, various roving glasses manufactured by Nippon Glass Fiber Co., Ltd. were used. The roving count of the roving glasses was as follows:
In Example 4, TEX2200 was used, in Comparative Example 4, TEX2100 was used, and in all other examples, TEX2310 was used.

The molding methods used for the molding materials obtained in each example were compression molding to prepare test pieces for confirming the strength of the molding material material and injection molding to prepare test pieces for measuring the strength of the product. Compression molding was carried out using a 300-ton press molding machine (manufactured by Kawaichi Hydraulic Co., Ltd.) equipped with a mold for making round flat plates with a diameter of 325 mm and a thickness of 3 mm, at a mold temperature of 150 to 160°C and a pressure of 100 kg/
The molding conditions were a 280mm x 255mm, ^3mm thick mold, and a curing time of 120 seconds. The injection molding was carried out using a BMC injection molding machine (manufactured by Ishikawajima-Harima Heavy Industries Co., Ltd., clamping force 200 tons, injection barrel diameter 70mmφ) set at a barrel temperature of 40°C.
The molding material is placed in the mold for creating the corner panel, and the mold temperature is 150-160
The molding conditions were: temperature 50°C, injection pressure 650 kg/cm ² , and curing time 60 seconds.

Example 1 A resin composition prepared by blending an unsaturated polyester resin with additives in the proportions shown in Table 1 and cut glass fiber bundles having the conditions shown in Table 1 were mixed and impregnated by the method described in Example 1 of DE 35 15 483 A1 to obtain a glass fiber reinforced unsaturated polyester resin molding compound (BMC). This molding material was used to produce round flat plates by compression molding and square panels by injection molding.
Physical properties were evaluated by impact testing. The compression-molded round plates were used to confirm the material strength, and the injection-molded square panels were used to measure the product strength. The test was performed by sampling the molded products as they were to create flatwise, unnotched test pieces, which were then subjected to an Izod impact test. The surface properties of the injection-molded products were evaluated by judging the appearance of the resulting square panels. The results are shown in Table 1. Note that all percentages in Table 1 are by weight.

Examples 2 to 4 Molding materials were produced in the same manner as in Example 1 using the resin compositions and cut glass fiber bundles shown in Table 1. Molding and testing were carried out in the same manner as in Example 1 using each of the resulting molding materials, with the results shown in Table 1. The corner panels obtained in Examples 1 to 3 had excellent appearances, with no fiber pattern appearing on the surface of the molded product. The corner panel obtained in Example 4 had a good appearance, although a very slight fiber pattern appeared on the surface of the molded product.

Comparative Example 1 Molding materials were produced by a conventional method using a double-arm kneader using the resin compositions and cut glass fiber bundles shown in Table 1. Molding and testing were carried out in the same manner as in Example 1 using the obtained molding materials, and the results shown in Table 1 were obtained.

Comparative Examples 2 to 4 Molding materials were produced in the same manner as in Example 1 using the resin compositions and cut glass fiber bundles shown in Table 1. Molding and testing were carried out in the same manner as in Example 1 using each of the resulting molding materials, with the results shown in Table 1. The corner panel obtained in Comparative Example 4 had a noticeable fiber pattern on the surface of the molded product, resulting in poor appearance.

INDUSTRIAL APPLICABILITY By using the fiber-reinforced thermosetting resin molding material of the present invention, injection or transfer molding can be carried out with minimal damage to the glass fibers while maintaining high productivity, and it is therefore possible to obtain revolutionary large molded products with good surface conditions that have the rigidity and impact strength required for automobile parts such as exterior panels, in particular, strength that is more than twice that of conventional BMC molded products.

──────────────────────────────────────────────────── Continued from the front page (56) References: JP 52-27495 (JP, A) JP 49-124165 (JP, A) JP 57-125222 (JP, A) Utility Model Application Publication No. 1983-115328 (JP, U)

Claims (9)

[Claims] 1. A molding material for hot-press molding by being introduced into a mold using a plunger or screw mechanism, the molding material comprising a liquid thermosetting resin composition containing a styrene monomer as a crosslinking component and cut glass fiber bundles,
The number of fibers in the glass fiber bundle is in the range of 600 to 1,400,
A fiber-reinforced thermosetting resin molding material characterized by using cut pieces of glass fiber bundles having a length of 6 to 25 mm, in which the binder adhesion amount of the glass fiber bundles is 1.0% by weight or more and the amount of insoluble components in the binder relative to the styrene monomer is in the range of 40 to 90% by weight. 2. The molding material according to claim 1, wherein the content of cut glass fiber bundles is 15 to 30% by weight. 3. The molding material according to claim 1, wherein the amount of binder attached is 1.0 to 2.3% by weight. 4. The binder according to claim 1, wherein the amount of insoluble components relative to the styrene monomer in the binder is in the range of 45 to 85% by weight.
The molding material according to item . 5. The molding material according to claim 4, wherein the length of the cut glass fiber bundles is 12 to 18 mm. 6. The molding material according to claim 4, wherein the content of cut glass fiber bundles is 15 to 25% by weight. 7. The molding material according to claim 4, wherein the amount of binder attached is 1.7 to 2.3% by weight. 8. The molding material according to claim 1, wherein the liquid thermosetting resin composition is an unsaturated polyester resin composition. 9. The molding material according to claim 1, which is a bulk molding compound.