KR920002381B1 - Preparation of glass fiber cloth prepreg - Google Patents

Abstract

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Description

Method for manufacturing prepreg of fiberglass cloth

The present invention relates to a method for producing prepreg of glass fiber cloth, in particular of belt-shaped glass fiber cloth.

As is known, a prepreg is a laminate material obtained by impregnating a thermosetting resin into a continuous reinforcement such as fabric, paper, mat, and the like, and then drying the impregnated material to B-step.

Here, the B-step refers to a step of a thermosetting resin in which the thermosetting resin swells in a liquid such as alcohol, acetone, etc., but is not completely dissolved and softens to a rubbery degree when the thermosetting resin is heated, but does not melt completely. Means. Usually, thermosetting resin is used for impregnation of glass fiber cloth or the like in the form of a varnish.

When the prepreg is manufactured from a target glass fiber cloth having a baffle end woven with a recent improved loom such as an air jet loom, the following problems occur.

The first problem is that the impregnated glass fiber cloth contains excess resin at its end, and the thickness of the end tends to be thicker than other parts. When prepregs having such thicker ends are cut into each of the same desired size and the cuts are stacked, the prepreg stack has a thicker thickness that forms a laminate of non-uniform thickness at its ends. . Thus, prepregs that do not have a uniform thickness throughout their widths cause various defects when the prepregs are processed into products. As an example, when using prepregs for the production of copper-clad laminates, it is not possible to apply pressure across the prepreg width.

The second problem is that when viewed in the longitudinal direction of the prepreg, both ends of the prepreg are not linear but irregular because of the baffle end. When the prepreg having such an uneven end is cut to the same required length and laminated with a cut, the end of the resulting prepreg laminate is hard to be trimmed, and when the end is trimmed, part of the uneven end is torn off, It is dispersed and mixed in the laminate, causing defective products.

A third problem is that during the manufacture of the prepreg, a portion of the fiberglass cloth ends tears, is mixed in the impregnation varnish, and adheres to the surface of the prepreg, causing defects.

Such a problem occurs when the prepreg is manufactured from a target fiberglass cloth having a fluff end. The first problem also arises with the end of the fiberglass cloth woven into the shuttle loom.

In order to overcome the first and second problems described above, the ends of the prepreg can be cut off and removed. In this case, the third problem still remains unresolved and also reduces the yield of glass fiber cloth and varnish, which is undesirable in terms of cost.

The end of the glass fiber cloth of interest can be removed before it is processed into prepregs. However, no suitable method has been developed. For example, Japanese Patent Laid-Open No. 34094/1977 discloses that when the width of the target fiber cloth is cut in the longitudinal direction and converted into a narrow glass fiber cloth, acrylic, polyvinyl acetate, A method of applying an adhesive of polyvinyl chloride resin or rubber, preferably an adhesive of polyvinyl acetate resin that is miscible with polyester resin, is proposed. However, it is doubtful whether this method is a suitable method for obtaining glass fiber cloth as a material for prepreg. In addition, even after the narrow glass fiber cloth is produced according to this method, it is impossible to obtain a satisfactory prepreg without the above problem even if the end thereof is removed. Further, Japanese Patent Laid-Open No. 18568/1973 proposes a method of impregnating a cut portion with a heat-sealing synthetic resin for preventing loosening when a particular knitted fabric or fabric is cut according to knitting or weaving. By this method, satisfactory prepregs cannot be obtained.

It is an object of the present invention to provide a prepreg of glass fiber cloth which is free from the drawbacks of the conventional techniques described above, has a uniform thickness across the entire width, and is linear at both ends and is not uneven, wherein the fibers at the ends are not teared. It does not adhere to other prepreg sites and does not cause any deterioration.

The present invention is to heat the inner portion of the end of the glass fiber cloth to remove the residual stress of the glass fiber in the glass fiber cloth, and then to the heat-treated portion of the glass fiber cloth insoluble in the thermosetting resin varnish saturated polyester of 150 ℃ to 180 ℃ After coating with a resin resin solution, the coating amount is less than 1 to 4% by weight based on the weight of the coated glass fiber cloth portion, and the resulting glass fiber cloth is dried, and the end of the glass fiber cloth is cut off and then removed. Impregnating the thermosetting resin varnish into the glass fiber cloth with the end removed under tension, and drying the impregnated glass fiber cloth retained under low tension, impregnating the glass fiber cloth with the thermosetting resin varnish. The present invention relates to a method of manufacturing a prepreg of glass fiber cloth by drying the fiber cloth.

Glass fiber cloth used in the method of the present invention is 25 to 300g / m ² , for example USMIL spec. Style No. 7641 (unit weight 297 g / m ² ), No. 7628 (203 g / m ² ), No. ^{2116 (109g / m 2),} No.1080 (48.5g / m 2), No. 106 (30 g / m ² ), No. And a unit weight of 104 (25 g / m ² ). However, the glass fiber cloth used is not limited thereto.

In the process of the present invention, the glass fiber cloth is cut off and removed before being impregnated in the thermosetting varnish. In order to maintain the original shape, the cut portion of the glass fiber cloth is coated with a synthetic resin in advance. Therefore, this resin should be resistant to the temperatures and varnishes used in prepreg manufacture. The strength of the coating resin for fixing the glass fibers around the cuts varies at each stage of prepreg production. This strength is weakest in the drying stage where the coating resin tends to soften under the influence of varnish and drying temperature. In this drying step, when the movement force of the engagement of the glass fiber cloth is larger than the fixing force of the coating resin described above, the shape of the cut portion of the glass fiber cloth is changed, whereby the cut portion is corrugated, and in the extreme case, the engagement at the cut portion is released. . If the glass fiber has residual stress at the cutout, the above-mentioned moving force is very large. Therefore, it is necessary to remove residual stress in advance of the glass fiber in the site | part covered with synthetic resin.

Compared with organic fibers, glass fibers have a large Young's modulus. As a result, the glass fibers in the glass fiber cloth have a large residual stress. When heated in an oven, fiberglass fabrics prepared by conventional weaving and post-treatment exhibit twisting at certain temperatures. The twist becomes even larger when each single fiber constituting the fiberglass cloth has a larger diameter and even when the fiberglass cloth has a larger number per inch of engagement and / or cross thread. Greater torsion is caused by greater residual stresses.

As mentioned above, the production of the prepreg from glass fiber cloth of large residual stress causes a change in the shape of the cut portion coated with the resin. That is, since the engagement around the cutout has a greater moving force than the fixing force of the coating resin, some of these engagements move along the cross yarns outside of the fabric and are separated from the cross yarns, which are prepped by the varnish in the protruding and corrugated state. It is fixed to the leg. When viewed along cuts that must be linear in theory, the engagement of these protruding and corrugated states forms a number of continuous or non-continuous waveforms. These waveforms become larger in amplitude and height when the fiberglass cloth exhibits greater torsion. In the extreme case, the protrusion and wave engagement are released.

Residual stress can be removed by heat treatment. For example, when the glass fiber cloth obtained by conventional weaving and post-treatment is heat-treated at 600 ° C. for 20 seconds, the glass fiber cloth after the heat treatment hardly causes the above-described distortion seen when it is heated. Therefore, when the prepreg is produced from the heat-treated glass fiber cloth, engagement of the cut portion of the prepreg does not become a wave, and the cut portion becomes almost linear.

Heat treatment conditions for removing the residual stress of the glass fiber cloth are arbitrary as long as the residual stress can be removed. Removal of residual stress can be seen by heating the fiberglass cloth in an oven and observing the twist. The heat treatment time can be shortened when high temperatures are used. Longer heating times require lower temperatures. The upper limit of the heat treatment temperature varies depending on the glass composition, but should be lower than the temperature when the glass fiber cloth becomes a fluid, that is, the glass transition temperature. The lower limit heat treatment temperature is preferably about 400 ° C. However, the heat treatment effect can be observed even at 250 ° C. With respect to the heat treatment time, the shortest time for reducing the residual stress to the desired state can be used. As a part of the glass fiber cloth heat-treated for removing residual stress, it is appropriate to coat this part with resin. In the heat treatment, a suitable method such as direct heating using a burner may be used. Preference is given to using jet heaters which continuously generate heated air of about 850 ° C. or less.

The glass fiber cloth from which the residual stress has been removed is coated with a resin dissolved in a solvent at the site where the residual stress has been removed, that is, at the inner side of the end portion. This resin must be insoluble in the thermosetting resin varnish used in the later stages, so that the fixing force of the resin for the glass fiber around the cut is not weakened by the varnish's dissolving power in the later process in which the varnish is impregnated with the glass fiber cloth from which the end is removed.

As the thermosetting resin used for impregnation of the glass fiber cloth for prepreg production, a large number of epoxy resins and polyimide resins are usually used. These resins may preferably be used in the present invention. These resins are used in the form of varnishes in which each resin is dissolved in a solvent. The solid resin content in the varnish is usually 40 to 70% by weight. After the glass fiber cloth is immersed in one of these thermosetting resin varnishes, the solvent in the varnish is removed by evaporation in a dryer to prepare a prepreg. The solid resin content in the prepreg is usually 40 to 70% by weight. As an example of a thermosetting resin varnish, 125 parts of an epoxy resin of the bisphenol A type [epoxy equivalent: 500, epoxy value (bromine content%): 0.20 to 0.22], 4.0 parts of dicyandiamide, 0.2 parts of benzyldimethylamine, 55 parts of acetone , Varnish consisting of 14.0 parts of dimethylformamide and 3.0 parts of water (hereinafter referred to as "G-10 varnish") may be mentioned.

Therefore, as the resin used to coat the inner part of the glass fiber cloth end in the present invention, a saturated polyester resin insoluble in the varnish of the thermosetting resin used for impregnation is selected.

In addition, saturated polyester resins should not be softened in a dryer at a drying temperature. It is preferable that this resin has a softening point as high as possible. However, the high softening point results in low solubility in the solvent, so the upper limit of the softening point is the highest softening point where the solubility of the resin in the solvent is maintained. Therefore, the range of the softening point measured by JISK2531 Ring and ball Method is 150-180 degreeC. If the softening point of the resin is less than 150 DEG C, the fixing force of the resin for the glass fiber around the cut portion becomes too weak in the drying step, and thus such a resin cannot be used.

As the preferred saturated polyester resin, a resin composed of 100 mol% of an acid component (14 mol% of isophthalic acid, 31 mol% of adipic acid and 55 mol% of terephthalic acid) and 100 mol% of a glycol component (1,4-dibutylene glycol) (Hereinafter referred to as "T-resin") may be mentioned.

As a solvent for saturated polyester resin used in the present invention, a solvent having low toxicity and low boiling point is preferable. Low boiling solvents can result in lower drying temperatures and also provide faster evaporation rates after coating. Therefore, the coating resin solidifies more quickly and no spreading occurs, so that a reliable coating is possible. As the low boiling point solvent, halogenated lower hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride and the like can be mentioned, for example.

The inventors of the present invention, when the amount of saturated polyester resin to be applied to the heat-treated portion of the glass fiber cloth is 4 to 10% by weight (based on the solid resin), the prepreg of the glass fiber cloth can be obtained to overcome the above-mentioned drawbacks of the prior art. Revealed.

As a result of further studies, the inventors have found that similar results are obtained when the amount of saturated polyester resin applied is less than 1 to 4% by weight when glass fiber cloth is maintained under low tension during impregnation with a thermosetting resin varnish and drying. It turns out that it can.

As described above, in the present invention, the glass fiber cloth is heat-treated at the inner side of its end to remove residual stress; The heat treated portion is coated with a saturated polyester resin solution and then dried; Cutting off the end; The resultant glass fiber cloth maintained under low tension is immersed in the thermosetting resin varnish according to a conventional method; Varnish-impregnated glass fiber cloths maintained under low tension were placed in a dryer and the solvent contained in the varnish was removed by evaporation to give a prepreg.

The low tension defined in the present invention is determined based on the following equation.

The value (kg / m) of low tension defined in the present invention = (thermosetting resin varnish-weight of impregnated glass fiber cloth) + (5 ± 3) tension is the tension of the prepreg manufacturing apparatus provided before the thermosetting varnish bath- It is controlled using a driving rool and a glass fiber-moving rool in the adjusting section.

In the present invention, the glass fiber cloth processed into the prepreg has its end removed before impregnation. Thus, the glass fibers at the ends tear and do not occur in the varnish used for impregnation. Substantially, the prepregs made according to the invention are cut into sheets of each identical dimension; These 2,000 sheets are stacked; The stack exhibits a uniform thickness throughout its width.

In the present invention, the glass fibers constituting the glass fiber cloth to be processed into the prepreg are removed from the residual stress at the heat treatment site of the glass fiber cloth. In addition, the heat treatment site is treated with a resin, whose fixing force for the glass fiber is not much weakened at a later stage of the glass fiber cloth impregnated with the varnish. Therefore, the cut portion of the glass fiber cloth maintains its shape and remains almost linear after the glass fiber cloth is processed into the prepreg. It is preferable to cut the prepreg prepared according to the invention into sheets of each same dimension and to align the ends of each stack in the substantial automatic manufacture of the copper laminates stacking sheets, each stack being end It does not show fiber tear or waveform.

Hereinafter, an aspect of the present invention will be described.

Example 1

The glass fiber cloth (style 7628) made with the air jet loom is heat-treated at 600 ° C for 20 seconds on the inner side of the two ends. Subsequently, it is insoluble in the varnish on the epoxy resin (G-10) at room temperature so as to be 1.5% by weight based on the weight of the coated portion of the glass fiber cloth, measured by JIS K 2531 Ring and Ball Method, and 170 ° C. The heat treatment site of the glass fiber cloth was coated with a methylene chloride solution of saturated polyester resin (T-resin) having a softening point of about 10 mm in width. The coating site is dried at about 100 ° C. Thus, the coated portion is cut to obtain a glass fiber cloth of constant width from which the end portion is removed.

Under a tension of 10 kg / m (including the weight of the thermosetting resin varnish—impregnated glass fiber cloth), the glass fiber cloth is immersed in a G-10 varnish having a resin content of 43% by weight and dried to obtain a prepreg.

In this prepreg, the cut sites coated with resin were almost linearly good.

Comparative Example 1

Except not performing the heat treatment of Example 1, to prepare a prepreg of glass fiber cloth in the same manner as in Example 1.

In this prepreg, partial movement of glass fiber engagement occurred at the cut portion covered with resin, and these portion waveforms were obtained.

Comparative Example 2

A prepreg of glass fiber cloth is prepared in the same manner as in Example 1, except that the tension in the prepreg step is 20 kg / m (including the weight of the thermosetting resin varnish-impregnated glass fiber cloth).

In this prepreg, loosening of glass fiber engagement occurred at the end.

Comparative Example 3

A glass fiber cloth prepreg was prepared in the same manner as in Example 1 except that the coating amount of the saturated polyester resin (T-resin) solution was 0.8% by weight as a resin.

In this prepreg, movement of glass fiber engagement occurred at the cut site, and the cut site became a wave.

Claims (4)

After heat-treating the inner part of the end of the glass fiber cloth to remove residual stress of the glass fiber in the glass fiber cloth, the heat-treated portion of the glass fiber cloth was converted into a saturated polyester resin solution having a softening point of 150 ° C to 180 ° C in the thermosetting resin varnish. Coating, so that the coating amount is less than 1 to 4% by weight as a resin based on the weight of the coated glass fiber cloth portion, the resulting glass fiber cloth is dried, the ends of the glass fiber cloth are cut off and removed, and then maintained under low tension. Impregnating the thermosetting resin varnish into the glass fiber cloth from which the end was removed, and impregnating the glass fiber cloth with the thermosetting resin varnish, and drying the impregnated glass fiber cloth. A method for producing prepreg of fiberglass cloth. The method for producing a prepreg of glass fiber cloth according to claim 1, wherein the thermosetting resin is an epoxy resin or a polyimide resin for dry lamination. The method for producing a prepreg of glass fiber cloth according to claim 1, wherein the solvent of the saturated polyester resin solution is a halogenated lower hydrocarbon. The method of producing a prepreg of glass fiber cloth according to claim 1, wherein the heat treatment temperature of the glass fiber cloth is about 400 ° C. or more and the glass transition temperature or less.