JP2010189543A - Method for producing composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a composite material excellent in molding processability without limiting the type of a curable resin or a filler and the blending ratio, wherein the method can reduce a residual stress causing poor dimensional stability or a crack of the composite material by suppressing the difference of the shrinkage amount produced between the resin and the filler in the production process. <P>SOLUTION: In the method for producing a composite material containing a curable resin and a filler, an uncured curable resin is cured in a temperature atmosphere lower than a service condition temperature of the composite material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a composite material including a curable resin and a filler.

  FRP in which a curable resin is reinforced with reinforcing fibers of a filler is known as a typical composite material. Utilizing the advantages of light weight, high elasticity, and high strength, this FRP is used in various applications such as fishing rods, golf shafts, tennis rackets, and other sports materials, aircraft, ships, automobiles, structural materials, and rolls, etc. Used for applications.

  Here, as problems of composite materials represented by these FRPs, there are poor dimensional stability such as sink marks and warpage due to internal stress remaining in a molded product, and generation of cracks. There are two causes for the internal stress remaining in the molded product, one is the curing shrinkage accompanying the curing reaction of the curable resin, and the other is the thermal shrinkage during cooling.

  Curing shrinkage occurs as a result of the distance between molecules shortening due to cross-linking and the volume is reduced. From the viewpoint of suppressing the curing shrinkage, an epoxy resin having a relatively small amount of curing shrinkage is used. This epoxy resin is excellent in physical properties after curing, and is said to be optimal as a resin for FRP. However, even if the curing shrinkage of the curable resin is suppressed, if the internal stress is generated due to the thermal shrinkage at the time of cooling after curing, the dimensional stability is deteriorated and a crack is generated. Therefore, in order to eliminate problems such as poor dimensional stability and cracks caused by internal stress remaining in the molded product, it is necessary to prevent stress from remaining in the resin after cooling after curing. is there.

  For example, a liquid epoxy resin composition for casting containing a specific amount of a liquid epoxy resin, a polyoxypropylene diamine having an average molecular weight in the range of 270 to 1800 as a curing agent, and an inorganic filler is disclosed (patent) Reference 1). According to the invention of this Patent Document 1, it is said that by blending an inorganic filler in a resin, the thermal stress of the resin can be suppressed and the residual stress can be reduced.

  Also disclosed is an epoxy resin composition comprising 10 to 50 parts by mass of specific rubber fine particles, 100 parts by mass of an epoxy resin that is liquid at normal temperature, and a curing agent that is liquid at normal temperature (see Patent Document 2). According to the invention of Patent Document 2, it is said that residual stress in the resin can be absorbed by blending a rubber component with the epoxy resin.

  Moreover, the technique of releasing the residual stress in the molded article which consists of a composite material by mix | blending a glass capsule in material and damaging a glass capsule is disclosed (refer patent document 3).

  By the way, in a composite material using a transparent resin as the curable resin and a transparent filler such as glass fiber as the filler, the dimensional stability associated with the internal stress remaining in the resin is poor. In addition to the generation of cracks, there is a problem that the originally intended composite material with transparency cannot be obtained. In order to solve this problem, an attempt has been made to obtain a transparent composite material by blending a curable resin having refractive indexes close to each other and glass fiber (see Patent Document 4).

Japanese Patent Laid-Open No. 06-248059 Japanese Patent Laid-Open No. 08-27360 JP 2008-150271 A Japanese Patent Laid-Open No. 2005-8721

  As described above, as disclosed in Patent Documents 1 to 3, researches for improving the poor dimensional stability associated with internal stress remaining in the resin and the occurrence of cracks have been actively conducted. However, there are still many challenges. First, in the conventional method, the types of curable resin that can be used are limited, and the curable resin cannot be freely selected according to the application. Secondly, in the conventional method, since components other than the curable resin and the filler are blended, the viscosity of the uncured curable resin is increased, and the impregnation property of the uncured curable resin into the filler is increased. The moldability of the composite material deteriorates, such as problems. Thirdly, in the conventional method, a preferable blending ratio of the curable resin and the filler is limited, and almost no effect can be obtained except for the blending ratio. These problems are not limited to fiber-based fillers, and the same applies to composite materials using fillers such as plate-like fillers.

  Further, in a composite material using a transparent resin as a curable resin and a transparent filler such as glass fiber as a filler, the refractive index is simply approximated as disclosed in Patent Document 4. Even if the curable resin and the glass fiber to be blended are mixed, light is scattered by the refractive index gradient generated inside the resin, the transparency is significantly impaired, and a highly transparent composite material cannot be obtained.

In view of the above problems, the present inventors have found that the residual stress inside the resin and the refractive index gradient inside the resin are both due to the difference in shrinkage produced between the resin and the filler that occurs in the manufacturing process. I found out that it was caused.
Accordingly, an object of the present invention is to reduce the residual stress that causes poor dimensional stability and cracks of the composite material by suppressing the difference in shrinkage generated between the resin and the filler during the manufacturing process. It is a method, and it is providing the manufacturing method of the composite material which was excellent also in the moldability, without receiving the restriction | limiting of the kind and compounding ratio of curable resin and a filler.
In addition, when a transparent resin is used as the curable resin and a transparent filler such as glass fiber is used as the filler, the amount of shrinkage generated between the resin and the filler during the manufacturing process is reduced. By suppressing the difference, an object of the present invention is to provide a production method capable of suppressing a refractive index gradient inside a resin that causes a decrease in transparency and also obtaining a highly transparent composite material.

  The method for producing a composite material according to claim 1 is a method for producing a composite material comprising a curable resin and a filler, and comprising a composite material precursor comprising an uncured curable resin and the filler. A precursor preparing step to be prepared; and a curing step of curing the uncured curable resin contained in the composite material precursor in a temperature atmosphere lower than a use environment temperature of the composite material. And

  The method for producing a composite material according to claim 2 uses glass fiber as the filler in the precursor preparation step in the method for producing the composite material according to claim 1, and the composite material as the curable resin. A transparent resin having a refractive index at a use environment temperature of which approximates the refractive index of the glass fiber is used.

According to a third aspect of the present invention, there is provided a method for producing the composite material, wherein the uncured curable resin contained in the composite material precursor is the following in the curing step in the method for producing the composite material according to the first or second aspect. It is characterized by curing within the range of reaction temperature ± 15 ° C. represented by the formula (1).

According to invention of Claim 1, the hardening process which hardens | cures curable resin in the temperature atmosphere lower than the use environmental temperature of a composite material was provided. Thereby, the temperature of curable resin rises from the reaction temperature in the case of hardening to use environment temperature. When the temperature of the curable resin increases, the cured curable resin thermally expands. If the thermal expansion occurs, the shrinkage amount of the curable resin generated during curing is reduced, and the shrinkage amount during curing approaches the shrinkage amount of the filler smaller than that of the resin. During thermal expansion, the resin in the vicinity of the interface with the filler is suppressed by the filler, while the resin other than in the vicinity of the interface freely expands freely. The difference in shrinkage can also be eliminated. Therefore, the residual stress can be reduced by eliminating the difference between the shrinkage amount of the curable resin and the shrinkage amount of the filler, and it is possible to suppress the deterioration of the dimensional stability of the composite material and the occurrence of cracks. As a result, a composite material having high strength, high heat resistance, high flame retardancy, and high appearance can be provided, and can be used in various fields such as automobiles, electronic parts, and architecture.
In addition, according to the present invention, the above effect can be achieved by curing the curable resin in a temperature atmosphere lower than the use environment temperature of the composite material. And is excellent in moldability.

  According to the second aspect of the invention, the same effect as that of the first aspect of the invention can be obtained, and a composite material having higher transparency than the conventional one can be obtained. That is, by curing the curable resin in an atmosphere lower than the use environment temperature of the composite material, the temperature of the resin in the composite material rises from the reaction temperature at the time of curing to the use environment temperature. Since the resin expands thermally when the temperature of the resin rises, the shrinkage of the curable resin generated during curing is reduced, and the shrinkage during curing approaches the shrinkage of the filler smaller than that of the resin. The refractive index approaches. During thermal expansion, the resin in the vicinity of the interface with the filler is suppressed by the filler, while the resin other than in the vicinity of the interface freely expands freely. The difference in shrinkage can be eliminated, and the refractive index gradient inside the resin can also be eliminated. Therefore, the difference between the refractive index of the curable resin and the refractive index of the filler disappears, whereby the transparency of the composite material can be improved.

  According to the invention described in claim 3, by determining the reaction temperature using the above formula (1), the shrinkage amount of the curable resin and the shrinkage amount of the filler can be easily achieved at the use environment temperature of the composite material. And can be approached reliably. As a result, according to the present invention, the same effects as those of the first and second aspects of the invention can be obtained easily and reliably.

It is a figure for demonstrating the principle of residual stress suppression of this embodiment. It is a figure for demonstrating the principle of refractive index gradient suppression of this embodiment. It is a figure which shows the hardening process of the Example of this invention. It is a figure which shows the measurement result of the tensile strength and bending strength of an Example and a comparative example. It is a figure which shows the arithmetic mean wave | undulation of the composite material of an Example and a comparative example. It is a figure which shows the relationship between the temperature rise after hardening, and light transmittance.

  Hereinafter, modes for carrying out the present invention will be described.

<Production method of composite material>
The method for producing a composite material according to the present embodiment includes a precursor preparation step for preparing a composite material precursor including an uncured curable resin and a filler, and an uncured curable resin contained in the composite material precursor. And a curing step of curing in a temperature atmosphere lower than the use environment temperature of the composite material. Hereinafter, an example of the manufacturing method of the composite material of this embodiment is demonstrated.

[Precursor preparation step]
In the precursor preparation step, a composite material precursor including an uncured curable resin and a filler is prepared. The manufacturing method of the composite material of this embodiment is characterized in that various curable resins and various fillers can be used.
Examples of the preparation method include a method of including an uncured curable resin in the filler. More specifically, a composite material precursor is obtained by impregnating a fiber cloth with an uncured curable resin.
Moreover, the preparation method which includes a filler in uncured curable resin is mentioned. More specifically, a composite material precursor is obtained by mixing a filler such as glass fiber with an uncured curable resin.
Note that the surface of the filler may be pretreated by a conventionally known method so that the above-described impregnation and mixing can be sufficiently performed.

  The curable resin is not particularly limited as long as it can be cured in a temperature atmosphere lower than the use environment temperature of the composite material, and a conventionally known curable resin can be used. For example, a UV curable resin, a visible light curable resin, an electron beam curable resin, an anaerobic curable resin, a two-component curable resin, and the like can be given. That is, any curable resin that can be cured without heating may be used. Specifically, an epoxy resin, an acrylic resin, a vinyl ester resin, an unsaturated polyester resin, a urethane resin, or the like can be used. Depending on the type of resin, cationic polymerization initiators such as antimony compounds and iodine compounds, radical polymerization initiators such as benzophenone, organic peroxides and organometallic salts, and anaerobic polymerization accelerators such as dimethylaniline are appropriately used. Can be used.

It does not specifically limit as a filler, A conventionally well-known filler can be used. Conventionally known fillers include fibrous fillers, granular fillers, and plate-like fillers.
Examples of the fibrous filler include glass fiber, asbestos fiber, silica fiber, silica / alumina fiber, alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, and wollastonite. Examples thereof include inorganic fibrous materials such as silicate fibers, magnesium sulfate fibers, aluminum borate fibers, and metal fibrous materials such as stainless steel, aluminum, titanium, copper, and brass. A fiber cloth can also be used, and examples thereof include glass fiber base materials such as glass cloth, glass paper, and glass mat, woven cloth, non-woven cloth, and mats made of short glass fibers, glass filler, and synthetic fibers. The weaving method of the fiber cloth is not particularly limited, and any of plain weaving, Nanako weaving, satin weaving, twill weaving, and the like can be applied in the manufacturing method of this embodiment.
Examples of the granular filler include carbon black, graphite, silica, quartz powder, glass beads, milled glass fiber, glass balloon, glass powder, calcium silicate, aluminum silicate, kaolin, talc, clay, diatomaceous earth, and wollastonite. Silicates such as silicate, iron oxide, titanium oxide, zinc oxide, antimony trioxide, oxides of metals such as alumina, carbonates of metals such as calcium carbonate and magnesium carbonate, sulfates of metals such as calcium sulfate and barium sulfate, etc. Examples thereof include ferrite, silicon carbide, silicon nitride, boron nitride, and various metal powders.
Examples of the plate-like filler include mica, glass flakes, various metal foils, and the like.
Of the above fillers, fibrous fillers are particularly preferably used.

  In particular, in the composite material manufacturing method of the present embodiment, when glass fiber is used as the filler, and as the curable resin, a transparent resin whose refractive index at the use environment temperature of the composite material approximates the refractive index of the glass fiber is used. Can suppress a refractive index gradient generated in the resin while suppressing poor dimensional stability and generation of cracks due to internal stress remaining in the molded article, thereby obtaining a highly transparent composite material. The principle of reducing the residual stress and the principle of reducing the refractive index gradient will be described later.

As the transparent resin, a transparent resin such as an epoxy resin, an acrylic resin, a vinyl ester resin, or an unsaturated polyester resin can be used.
Here, “approximate” the refractive index means that the refractive index is the same and includes a case where there is a slight difference in the refractive index within a range that does not affect the transparency.

[Curing process]
In the curing step, the uncured curable resin contained in the composite material precursor is cured. The curing step of this embodiment is characterized in that curing is performed in an atmosphere having a temperature lower than the use environment temperature of the composite material. In addition, hardening is performed by irradiating UV, visible light, etc. according to the kind of curable resin.
Here, the composite material obtained by the manufacturing method of the present embodiment can be applied to various uses, and the “use environment temperature of the composite material” means that the composite material is exposed in each of these uses. It means temperature. For example, when the composite material is used for a structural member of an automobile, the use environment temperature is −40 to 80 ° C.

Hereinafter, the effect of this embodiment will be described while explaining the principle of residual stress reduction in the manufacturing method of this embodiment.
FIG. 1 (a) schematically shows the relationship between the shrinkage of the filler and the shrinkage of the curable resin before curing. As shown to Fig.1 (a), since resin has fluidity | liquidity before hardening, the whole is a uniform state.

  FIG. 1B schematically shows the relationship between the shrinkage of the filler and the shrinkage of the curable resin immediately after curing. As shown in FIG. 1B, immediately after curing, the amount of shrinkage of the curable resin increases due to curing shrinkage due to the curing reaction of the curable resin. However, in the curable resin near the interface with the filler, the shrinkage in curing is suppressed by the filler, and therefore the increase in the shrinkage is small.

FIGS. 1C and 1D schematically show the relationship between the shrinkage of the filler and the shrinkage of the curable resin when placed at the use environment temperature after curing. FIG.1 (c) is a figure when it hardens | cures in temperature atmosphere higher than use environment temperature, ie, the case where it manufactures with the conventional manufacturing method, FIG.1 (d) is lower than use environment temperature. It is a figure at the time of making it harden | cure in a temperature atmosphere, ie, the case where it manufactures with the manufacturing method of this embodiment.
As shown in FIG. 1 (c), when curing is performed in a temperature atmosphere higher than the use environment temperature as in the past, the temperature of the curable resin is from the reaction temperature during the cure to the use environment temperature. descend. Since the curable resin causes thermal shrinkage due to this temperature decrease, the shrinkage amount of the curable resin further increases. As a result, the difference between the amount of shrinkage of the filler and the amount of shrinkage of the curable resin is further increased, and the amount of shrinkage is also large because the degree of shrinkage is different between the vicinity of the interface with the filler inside the resin and the rest. Differences occur and the internal stress remaining in the resin further increases. For this reason, the dimensional stability is deteriorated and cracks are generated, and a high-strength composite material cannot be obtained. Further, surface irregularities become conspicuous, and the appearance is also deteriorated.
On the other hand, as shown in FIG. 1 (d), when curing is performed in a temperature atmosphere lower than the use environment temperature as in this embodiment, the temperature of the curable resin is determined from the reaction temperature at the time of curing. It rises to the operating environment temperature. When the temperature of the curable resin increases, the cured curable resin thermally expands. If the thermal expansion occurs, the shrinkage amount of the curable resin generated during the curing is reduced, and the shrinkage amount during the curing approaches the shrinkage amount of the filler smaller than that of the resin. During thermal expansion, the resin in the vicinity of the interface with the filler is suppressed by the filler, while the resin other than in the vicinity of the interface freely expands freely. The difference in shrinkage can also be eliminated. Therefore, the difference between the shrinkage amount of the curable resin and the shrinkage amount of the filler disappears, so that the residual stress can be reduced, and the deterioration of the dimensional stability of the composite material and the occurrence of cracks can be suppressed. As a result, it is possible to provide a composite material having high strength, high heat resistance, high flame retardancy, and high appearance, and can be used in various fields such as automobiles, electronic parts, and architecture.
In addition, according to the present embodiment, since the above effect can be achieved by curing the curable resin under a temperature atmosphere lower than the use environment temperature of the composite material, the type and blending ratio of the curable resin and the filler There is no restriction, and the moldability is excellent.

Next, in the manufacturing method of the present embodiment, refraction when glass fiber is used as a filler and a transparent resin whose refractive index at the use environment temperature of the composite material approximates the refractive index of the glass fiber is used as the curable resin. The effect of this embodiment will be described while explaining the principle of rate gradient reduction.
FIG. 2 (a) schematically shows the relationship between the refractive index of the glass fiber and the refractive index of the curable resin before curing. As shown in FIG. 2 (a), since the resin has fluidity before curing, the entire refractive index is in a uniform state.

  FIG. 2B schematically shows the relationship between the refractive index of the glass fiber and the refractive index of the curable resin immediately after curing. As shown in FIG. 2 (b), immediately after curing, the shrinkage due to the curing reaction of the curable resin increases the amount of shrinkage of the curable resin and increases the density, so that the refractive index increases. However, in the curable resin near the interface with the filler, the shrinkage in curing is suppressed by the filler, so that the increase in shrinkage is small and the refractive index is not so high.

FIGS. 2C and 2D schematically show the relationship between the refractive index of the glass fiber and the refractive index of the curable resin when placed at the use environment temperature after curing. FIG. 2 (c) is a diagram in the case of curing in a temperature atmosphere higher than the use environment temperature, that is, a case where it is produced by a conventional production method, and FIG. 2 (d) is a temperature atmosphere lower than the use environment temperature. It is a figure at the time of making it harden under, ie, the case where it manufactures with the manufacturing method of this embodiment.
As shown in FIG. 2 (c), when curing is performed in a temperature atmosphere higher than the use environment temperature as in the past, the temperature of the curable resin is decreased from the temperature at the time of curing to the use environment temperature. To do. Since the curable resin causes thermal shrinkage due to this temperature decrease, the refractive index of the curable resin is further increased. As a result, the difference between the refractive index of the glass fiber and the refractive index of the curable resin is further increased, and the amount of shrinkage is also different because the degree of shrinkage is different between the vicinity of the interface with the filler inside the resin and other areas. A large difference will result in a larger refractive index gradient and the transparency of the composite will be significantly reduced.
On the other hand, as shown in FIG. 2 (d), when the curing step is performed in a temperature atmosphere lower than the use environment temperature as in this embodiment, the curable resin is used from the reaction temperature during the cure to the use environment temperature. Temperature rises. When the temperature of the curable resin rises, the cured curable resin thermally expands. If the curable resin thermally expands, the amount of shrinkage of the curable resin that occurs during curing is reduced, and the amount of shrinkage during curing approaches the amount of shrinkage of the filler smaller than that of the resin, so the refractive index also approaches. . During thermal expansion, the resin in the vicinity of the interface with the filler is suppressed by the filler, while the resin other than in the vicinity of the interface freely expands freely. The difference in shrinkage can be eliminated, and the refractive index gradient inside the resin can also be eliminated. Therefore, the difference between the refractive index of the curable resin and the refractive index of the filler disappears, whereby the transparency of the composite material can be improved.

In addition, in the manufacturing method of this embodiment, although hardening of curable resin is performed in the temperature atmosphere lower than the use environment temperature of a composite material, moreover, reaction temperature computed by following formula (1) Curing is preferably performed within a range of ± 15 ° C. When the reaction temperature is within the range of ± 15 ° C. obtained from the following formula (1), there is not much difference in the light transmittance of the composite material, and high transparency is obtained.

In consideration of the fact that the physical properties that affect the shrinkage and expansion of the resin are the amount of cure shrinkage and the linear expansion coefficient, the formula (1) takes into account that a semi-cured state is also included in the cure shrinkage. It is derived by setting a coefficient.
In Equation (1), the temperature at which the composite material is actually used is substituted for the use environment temperature. The curing shrinkage rate and linear expansion coefficient of the curable resin are specific to the resin, and the measurement method is not particularly limited. For example, the value measured by the method described in the Example mentioned later can be substituted.

  By determining the reaction temperature using the above equation (1), the shrinkage amount of the curable resin and the shrinkage amount of the filler can be easily and reliably brought close to each other at the use environment temperature of the composite material. Therefore, the effects described above are easily and reliably achieved.

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples. The various measurement items in the examples were determined as follows.

In this example, the following glass fiber was used as the filler.
<Filler>
Glass fiber 1: Glass cloth ("7628/1260 / AS891AW" manufactured by Asahi Kasei Electronics Co., Ltd., basis weight = 200 g / m ² × 9 ply)
Glass fiber 2: Non-crimp fabric (“S32EX010-00600-01270-250,000”, manufactured by SEATEX), basis weight (600 g / m ² × 3ply)
Glass fiber 3: Non-woven fabric, basis weight (600 g / m ² × 3 ply)
Glass fiber 4: Glass cloth (“1080/1060 / AS891MSW”, manufactured by Asahi Kasei Microdevices Corporation)
Glass fiber 5: Glass cloth (“1080/1060 / AS891AW”, manufactured by Asahi Kasei Electronics)
Glass fiber 6: Glass cloth (“1080/1270 / AS750”, manufactured by Asahi Kasei Electronics)
Glass fiber 7: Glass cloth ("WLA 180 M 110 H974", manufactured by Nittobo)
Glass fiber 8: Glass cloth (“WF230 100 BS6”, manufactured by Nittobo)

In this example, the following resin was used as the curable resin. The amount of cure shrinkage and the linear expansion coefficient are values measured according to the measurement method described later. Moreover, the following acrylic resin and epoxy resin are adjusted so that the refractive index at room temperature (25 ° C.) matches the refractive index of the glass fiber in the state of a cured product.
<Curable resin>
Acrylic resin: UV curable acrylic resin (“Diabeam” manufactured by Mitsubishi Rayon Co., Ltd., curing shrinkage 6.7%, linear expansion coefficient 345 × 10 ⁻⁶ / K)
Epoxy resin: UV curable epoxy resin (manufactured by NTT Advanced Technology, cure shrinkage 3.8%, linear expansion coefficient 107 × 10 ⁻⁶ / K)

[Measurement of cure shrinkage]
The cure shrinkage rate of the curable resin was determined as follows.
First, the specific gravity of the uncured and liquid curable resin was measured. For the measurement, a vibrating liquid density meter (“DAM48” manufactured by Antompaar) was used. This uncured and liquid curable resin was cured under the same conditions and method as those described later (Example 1 for acrylic resin, Example 2 for epoxy resin). The obtained resin plate having a thickness of 2 mm was cut into 30 mm × 30 mm with a diamond cutter, and the specific gravity of the cut resin pieces was measured. A specific gravity meter (“AUW-D-SGM” manufactured by Shimadzu Corporation) was used for the measurement. Then, the specific gravity of the uncured resin and the specific gravity of the cured resin were substituted into the following formula (2) to determine the cure shrinkage.

[Measurement of linear expansion coefficient]
The linear expansion coefficient of the curable resin was determined as follows.
A resin plate having a thickness of 2 mm obtained in the same manner as the measurement of the curing shrinkage rate was cut out to 5 mm × 5 mm with a diamond cutter. Subsequently, the linear expansion coefficient of the cut resin piece was measured using a TMA measuring apparatus (“TMA / SS6300” manufactured by SII Nano Technology).

<Example 1>
[Precursor preparation step]
First, pretreatment of the glass cloth was performed. Specifically, the glass cloth was heated at 400 ° C. for 30 hours to remove organic components on the surface of the glass cloth. Thereafter, a glass cloth was immersed in a solution obtained by diluting a silane coupling agent (“KBM-503” manufactured by Shin-Etsu Silicon Co., Ltd.) 100 times with ethanol. After immersion, the glass cloth was taken out from the solution and dried at 100 ° C. for 1 hour.
Next, the glass cloth was impregnated with the uncured acrylic resin by immersing the pretreated glass cloth in the uncured acrylic resin and vacuum degassing. The glass cloth impregnated with the uncured acrylic resin was sandwiched between two glass plates adjusted so that the interval at the time of superposition was 2 mm, and excess uncured acrylic resin was removed from the glass cloth. As a result, a composite material precursor 1 sandwiched between glass plates having a fiber volume content of 45% was obtained.

[Curing process]
The composite material precursor 1 was put in a plastic bag that did not allow water to pass through, and as shown in FIG. 3, the plastic bag was submerged in a water tank filled with 5 ° C. water, and the composite material precursor 1 was cooled. After cooling, the composite material precursor 1 was irradiated with UV through water, a plastic bag, and a glass plate to cure the uncured acrylic resin. For UV irradiation, a UV irradiator (“Handy Cure” manufactured by Sen Special Light Source Co., Ltd.) was used, and irradiation was performed with an irradiation intensity of 50 mW / cm ² and an irradiation time of 30 minutes. After the irradiation, the composite material 1 sandwiched between the glass plates was taken out from the plastic bag, and the glass plate was removed to obtain a composite material 1 having a thickness of 2 mm.
The reaction temperature of 5 ° C. for the curing reaction was calculated by substituting the curing shrinkage rate and linear expansion coefficient of the acrylic resin into the above formula (1), assuming that the use environment temperature of the composite material is 25 ° C.

<Comparative Example 1>
A composite material precursor 1 sandwiched between glass plates was produced by the same method as in Example 1. The composite material precursor 1 was heated and held at 100 ° C. using a hot plate. Next, the composite material precursor 1 was irradiated with UV to cure the uncured acrylic resin. In addition, the apparatus similar to Example 1 was used for UV irradiation, and irradiation was performed on the conditions of irradiation intensity 50mW / cm < ² > and irradiation time 10 minutes. After irradiation, the sample was cooled, and the glass plate was removed to obtain a composite material 2 having a plate thickness of 2 mm.

<Example 2>
A composite material precursor 2 was produced in the same manner as in Example 1 except that the acrylic resin was changed to the epoxy resin and the water temperature in the water tank in the curing step was changed to 20 ° C., and a composite material 3 was obtained. However, since the glass cloth was subjected to a surface treatment for epoxy, pretreatment was omitted.
The reaction temperature of 20 ° C. for the curing reaction was calculated by substituting the curing shrinkage rate and the linear expansion coefficient of the epoxy resin into the above formula (1), assuming that the use environment temperature of the composite material is 25 ° C.

<Comparative example 2>
A composite material precursor 2 was produced in the same manner as in Example 2. The composite material precursor 2 was irradiated with UV at room temperature. For UV irradiation, the same apparatus as in Example 1 was used, and irradiation was performed under conditions of an irradiation intensity of 50 mW / cm ² and an irradiation time of 10 minutes. After the irradiation, the composite material precursor 2 was further cured by heating in a thermostat kept at 80 ° C. for 1 hour. Next, the sample was cooled, and the glass plate was removed to obtain a composite material 4 having a plate thickness of 2 mm.

<Example 3>
A composite material 5 was obtained in the same manner as in Example 2 except that the glass cloth was changed to the non-crimp fabric (hereinafter also referred to as NCF).

<Comparative Example 3>
A composite material 6 was obtained in the same manner as in Comparative Example 2 except that the glass cloth was changed to the NCF.

<Example 4>
A composite material 7 was obtained in the same manner as in Example 2 except that the glass cloth was changed to the nonwoven fabric.

<Comparative example 4>
A composite material 8 was obtained in the same manner as in Comparative Example 2 except that the glass cloth was changed to the nonwoven fabric.

<Example 5>
Composite materials 9-1 to 9-4 were obtained in the same manner as in Example 2 except that the thickness of the fiber bundle of the glass cloth used in Example 2 was changed. 9-1 is produced using glass fiber 4, 9-2 is produced using glass fiber 1, 9-3 is produced using glass fiber 7, and 9-4 is produced using glass fiber 8. did.

<Comparative Example 5>
Composite materials 10-1 to 10-5 were obtained in the same manner as in Comparative Example 2, except that the thickness of the fiber bundle of the glass cloth used in Comparative Example 2 was changed. 10-1 is produced using glass fiber 4, 10-2 is produced using glass fiber 5, 10-3 is produced using glass fiber 6, and 10-4 is produced using glass fiber 1. And 10-5 was produced using the glass fiber 7.

<Evaluation of tensile strength>
About each composite material of Examples 1-2 and Comparative Examples 1-2, using a tensile tester ("5567" manufactured by INSTRON), in accordance with JIS K7054, the test piece shape is 200 mm x 10 mm x 2 mm, and the speed is 1 mm. The tensile strength was measured under the measurement conditions per minute. The measurement results are shown in FIG.

  As shown in FIG. 4A, the tensile strength of Example 1 in which the acrylic resin was cured at 5 ° C. was improved by 16% relative to the tensile strength of Comparative Example 1 in which the acrylic resin was cured at 100 ° C. It was confirmed. Further, it was confirmed that the tensile strength of Example 2 in which the epoxy resin was cured at 20 ° C. was improved by 5% relative to the tensile strength of Comparative Example 2 in which the epoxy resin was cured at 100 ° C. Therefore, it was confirmed that the composite material obtained by the manufacturing method of this example has improved tensile strength as compared with the conventional composite material.

<Evaluation of bending strength>
About each composite material of Examples 1-2 and Comparative Examples 1-2, using a bending tester ("5567" manufactured by INSTRON), in accordance with JIS K7017, the test piece shape is 60 mm x 15 mm x 2 mm, and the speed is 5 mm. The bending strength was measured under the measurement conditions per minute. The measurement results are shown in FIG.

  As shown in FIG. 4B, the bending strength of Example 1 in which the acrylic resin was cured at 5 ° C. was improved by 28% relative to the bending strength of Comparative Example 1 in which the acrylic resin was cured at 100 ° C. It was confirmed. Further, it was confirmed that the bending strength of Example 2 in which the epoxy resin was cured at 20 ° C. was improved by 10% with respect to the bending strength of Comparative Example 2 in which the epoxy resin was cured at 100 ° C. Therefore, it was confirmed that the composite material obtained by the manufacturing method of this example has improved bending strength as compared with the conventional composite material.

<Evaluation of surface swell>
The surface waviness of the composite materials 9-1 to 9-4 of Example 5 and the composite materials 10-1 to 10-5 of Comparative Example 5 was evaluated. Specifically, for each composite material, the surface waviness was measured by a method according to JIS B0601 using a surface roughness measuring machine (“SV-3000CNC” manufactured by Mitutoyo Corporation), and the arithmetic average waviness Wa was obtained. The results are shown in FIG.

  As shown in FIG. 5, in Example 5 in which the epoxy resin was cured at 20 ° C., the swell of the composite material surface was significantly reduced as compared with Comparative Example 5 in which the epoxy resin was cured at 80 ° C. It was confirmed. Thereby, according to the manufacturing method of the present example, it was found that even when the fiber bundle of glass fibers is thick, the undulation of the surface of the composite material can be suppressed, and the number of fiber bundles can be reduced to improve the moldability. . The numbers in FIG. 5 indicate that the glass fibers used are those shown in Table 1.

<Evaluation of transparency>
About each composite material of Examples 1-4 and Comparative Examples 1-4, the haze value was measured at the measurement environment temperature of 25 degreeC using the haze meter ("HGM-2DP" by Suga Test Instruments Co., Ltd.). The measurement results are shown in Table 1.

As is clear from Table 1, it was confirmed that the transparency of the composite material was remarkably improved according to the production method of this example as compared with the comparative example. Specifically, the haze value can be reduced by about 50% in the present embodiment compared to the comparative example, and the transparency (level haze value of 9.1% when the plate thickness is 2 mm and the fiber volume content is 45% is not possible in the past). (Example 2)) was obtained.
In particular, from the results of Examples 1 and 2 and Comparative Examples 1 and 2, it was confirmed that the transparency was improved regardless of the type of resin. Moreover, from the results of Examples 2 to 4 and Comparative Examples 2 to 4, it was confirmed that the transparency was improved regardless of the form of the filler such as glass fiber.

<Evaluation of reaction temperature>
According to the following procedure, the composite materials of Comparative Example 1 and Comparative Example 2 were used to evaluate the optimum reaction temperature for each resin, that is, the validity of the above formula (1).
First, a composite material of Comparative Example 1 in which an acrylic resin was cured at 100 ° C. and Comparative Example 2 in which an epoxy resin was cured at 80 ° C. was measured using a spectrophotometer (“U-4000” manufactured by Hitachi High-Tech). The transmittance was measured. In the measurement, the light transmittance at each measurement temperature was measured by changing the measurement temperature. The measurement results are shown in FIGS. 6 (a) and 6 (b), respectively. In each figure, the horizontal axis indicates the temperature rise (K) and the vertical axis indicates the light transmittance. In FIG. 6, the point with the highest light transmittance was defined as the point where the refractive index gradient of the curable resin disappeared.

From FIG. 6A, it can be seen that a temperature increase of 20 ° C. is necessary after curing in order to obtain the highest light transmittance in the composite material using the acrylic resin. That is, when the use environment temperature is 25 ° C., it means that the highest light transmittance is obtained when the reaction temperature is 5 ° C. This coincided with the optimum reaction temperature obtained by the above formula (1), and the validity of the formula (1) was proved.
For acrylic resins, it was confirmed that the difference in light transmittance was small in the range of temperature rise of 20 ° C. ± 15 ° C. and the transparency was not significantly affected.
On the other hand, FIG. 6 (b) shows that a temperature increase of 5 ° C. is necessary after curing in order to obtain the highest light transmittance in the composite material using the epoxy resin. That is, when the use environment temperature is 25 ° C., it means that the highest light transmittance is obtained when the reaction temperature is 20 ° C. This coincided with the optimum reaction temperature obtained by the above formula (1), and the validity of the formula (1) was proved.

Claims (3)

A method for producing a composite material including a curable resin and a filler,
A precursor preparation step of preparing a composite precursor including an uncured curable resin and the filler;
A curing step of curing the uncured curable resin contained in the composite material precursor in a temperature atmosphere lower than a use environment temperature of the composite material. In the precursor preparation step,
The glass fiber is used as the filler, and a transparent resin having a refractive index at a use environment temperature of the composite material approximate to a refractive index of the glass fiber is used as the curable resin. A method for producing a composite material. In the curing step,
The said uncured curable resin contained in the said composite material precursor is hardened within the range of reaction temperature +/- 15 degreeC represented by following formula (1), It is characterized by the above-mentioned. A method for producing a composite material.

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