JPH0156085B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a varnish used for producing a photocurable prepreg tape. In general, a photocurable prepreg tape is completely cured by winding it around an article and irradiating it with light, so it is suitable for binding articles with a large heat capacity. It is also effective for items for which heating is inappropriate. The present invention relates to a method for producing a varnish composition used to produce such a prepreg.

Photocurable prepreg can be made by impregnating a base material such as glass tape with photocurable varnish. In this case, the properties required for the prepreg are (1) the surface of the prepreg tape is non-sticky and has excellent processing workability, such as being flexible and able to be sufficiently tightened when wrapped around an article.
(2) It cures quickly when exposed to light, and the cured product has excellent mechanical properties (creep resistance, strength, etc.), heat resistance, and oil resistance. (3) Naturally, it is also required to be inexpensive. In order to produce a prepreg that satisfies all of these requirements, it is extremely important to develop an excellent photocurable varnish.

As a result of intensive research, the present inventors have developed a method for producing a varnish for photocurable prepreg that satisfies the above-mentioned requirements to a high level.

That is, in the present invention, after reacting an epoxy resin containing 10 to 40 phr of polyvinyl formal or phenoxy resin or a mixed polymer of both at a temperature of 150 to 230°C, in the presence of a solvent, 0.7 to 40 phr per 1 epoxy equivalent is reacted. Blend 1.2 equivalents of (meth)acrylic acid, a small amount of polymerization inhibitor, and an epoxy ring-opening catalyst to reduce the acid value.
After reacting until it becomes 10 or less, add photosensitizer 0.05~
The gist is a method for producing a varnish composition for a photocurable prepreg tape containing 5% by weight.

The structure and varnish manufacturing method of the present invention will be explained below. Note that the photocurable varnish referred to in the present invention refers to a base resin with photocurable ability dissolved in a volatile solvent, and is different from the photocurable paint, which has many documents in the painting field. . That is, the photocurable paint used in the painting field is a solvent-free type consisting of an unsaturated prepolymer/monomer system, and even if the composition itself is impregnated into a glass substrate, the prepreg state described above cannot be obtained. This is because it cannot be done.

The present invention is directed to a varnish composition prepared by dissolving a base resin in which epoxy acrylate is modified with a specific linear polymer in a volatile solvent. To explain epoxy acrylate here, the resin refers to a vinyl ester obtained by adding acrylic acid or methacrylic acid to a so-called epoxy resin having two or more epoxy groups in the molecule. ,"Epoxy resin"
Issued on September 30, 1970, published by Shokodo, those listed can be used without any special restrictions.
Such epoxy acrylates are highly viscous to semi-solid prepolymers, and good prepregs cannot be made from varnishes based on these prepolymers. The reason for this is that the prepreg is sticky and has extremely poor workability. This is also because the adhesive strength is low and the prepreg tape tends to come apart. The present inventors have found that in order to improve this drawback, it is sufficient to partially blend a linear polymer. However, many linear polymers have poor compatibility with epoxy acrylates, causing them to separate when made into varnishes, and when made into prepregs, they become cloudy and their photocuring ability is significantly reduced. Many things happened. As a result of intensive studies under these circumstances, the present inventors discovered that linear polymers such as polyvinyl formal or phenoxy resin, which are highly polar and have functional groups such as hydroxyl groups in their molecules, can be used as epoxy acrylate. It was found that a varnish blended with varnish formed a relatively good prepreg. However, when such a linear polymer is used, the varnish gradually undergoes phase separation within the long groups (it becomes gelled in appearance in about 10 to 14 days) and is no longer impregnated into the substrate. Therefore, the present inventors conducted further studies and as a result, arrived at the present invention. Such a phenomenon is remarkable when polyvinyl formal is used. In addition, in any blend system, the photocured product is not a complete three-dimensional network structure, but rather an aggregate in which crosslinked polymers and linear polymers coexist; For example, linear polymers are extracted. This is disadvantageous in terms of chemical resistance, etc., and there is also a need for improvement in terms of a decrease in elastic modulus at high temperatures due to a decrease in crosslinking density of the cured product system. In other words, varnishes based on epoxy acrylate (B) synthesized using polyvinyl formal or phenoxy resin reacted with epoxy resin at a predetermined temperature (A) can prevent phase separation and last for a long time. The varnish can be made stable over a long period of time, and the properties of the cured product, such as a high elastic modulus at high temperatures, are superior to blends. This is thought to be due to the chemical bonding between the linear polymer and the prepolymer occurring as a modification effect due to the use of A as a starting material. The basis for this is an increase in rubber elastic modulus.

Next, polyvinyl formal, phenoxy resin, and their blending amounts will be explained. A prepreg made from a varnish using polyvinyl formal has a cured product that is highly flexible and strong. On the other hand, when phenoxy resin is used, a hard cured product with extremely high hardness is obtained. Therefore, both resins can be selected depending on the use and purpose, and if they are used together, it is convenient to prepare a wide variety of cured products. The blending ratio of these linear polymers to the epoxy resin is preferably selected within the range of 10 to 40 phr. If the blending amount is less than 10 phr, the final prepreg produced tends to have stickiness on the surface, which is not preferable. on the other hand
If it is blended in an amount of 40 phr or more, the viscosity of the varnish becomes extremely high, making it necessary to increase the degree of dilution of the solvent, resulting in a varnish with a low solid content, which is not preferable.

The preparation of the agent (A) is carried out as follows. Polyvinyl formal or phenoxy resin is gradually added to and dissolved in the epoxy resin charged in a conventional varnish production pot while stirring. In this case, the polymer may be provided in the form of a solid powder or pellet, or it may be provided in the form of a solvent in which it is preliminarily dissolved in a solvent. In the former case, the contents are gradually heated to uniformly dissolve. In the latter case, the solvent is distilled off while increasing the temperature. The temperature is raised while homogeneously dissolving the mixture, and finally, heating is continued for several hours at a high temperature of 150 to 230°C to prepare the above A.

A thus obtained is a mixed system of an epoxy resin (a), a linear polymer (b), and a partial reactant of a and b (c). If the operating temperature is lower than 150° C., the varnish that is finally obtained will have a tendency similar to that of the blend system described above, which is not preferable. On the other hand, if the temperature is higher than 230°C, the epoxy resins will react with each other, which may cause gelation, which is not preferable. Therefore, it is particularly preferable to carry out the reaction at 160 to 210°C for 3 to 5 hours. The thus obtained A is a mixture of a, b and c as described above. Here A
This section describes the results of the study on the situation of mixtures. For example, 100g of bisphenol A type epoxy resin (Ciel Kagaku, trade name Epicote 828, molecular weight approx. 380, epoxy equivalent weight approx. 190) and 30g of polyvinyl formal (PVF) (Chitsuso Co., Ltd., trade name Vinyretsu F, E type molecular weight approx. 43000). ℃4
For A, which was allowed to react for a long time, methanol, which is a poor solvent for PVF and a good solvent for Epicote 828, was added to precipitate PVF, and this precipitate was thoroughly washed with methanol and dried in vacuum. The weight of the precipitate thus treated is approximately 7
It showed an increase in g. Next, the precipitate was subjected to an extraction operation using methyl ethyl ketone, which is a strong solvent for epoxy resin, and about 5 g of Epicote 828 was extracted. These facts indicate that agent A is a mixture of a, b, and c as mentioned above, and that a considerable amount of epoxy resin is contained in the PVF precipitate. It shows. According to polymer solution theory,
Macromolecules, which are large molecules, form entangled bonds in concentrated solutions, and these entanglements cannot be easily disentangled. In this agent (A) according to the present invention, it is thought that such entanglement also occurs between PVF, which is a macromolecule, and between PVF and the epoxy resin, which is a prepolymer. This is thought to be the reason why a considerable amount of epoxy resin was contained in the precipitate. It is thought that by using such agent A, the affinity between the constituent components of the varnish is improved, and as a result, a photocurable varnish with good compatibility is produced. The temperature of the agent A prepared as described above is then lowered to about 100° C., and the following solvent is added to reduce the viscosity, and at the same time, meth(acrylic) acid is added to synthesize epoxy acrylate. The above specific linear polymer is used as the solvent.
In the case of PVF, especially aromatic hydrocarbons (e.g.
80 to 60 parts by weight of benzene, toluene, xylene, styrene, ethylbenzene, diethylbenzene, and isopropylbenzene, etc.) and alcohol (such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, and It is preferable to use 20 to 40 parts by weight of a mixed solvent (butanol, n-amyl alcohol, etc.). Aromatic hydrocarbons alone or alcohols alone cannot dissolve agent A homogeneously. However, if a mixed solvent is used within the above composition range, a homogeneous solution can be obtained.

In the case of an agent using a phenoxy resin, in addition to the above mixed solvent, ketones (e.g., acetone, methyl ethyl ketone, methyl-n-propyl ketone, methyl-n-butyl ketone) acetals (e.g., dioxane, furfural, tetrahydrofuran) are used. It is also possible to use various solvents such as. On the other hand, when PVF is used, it is known as a good solvent for the polymer. For example, dioxane, tetrahydrofuran, etc. initially give a homogeneous varnish, but precipitation of PVF occurs within several hours to several days, and the varnish appears to be in a gelled state with no fluidity, which is not preferred. Furthermore, since the varnish of the present invention volatilizes the solvent when producing the prepreg, it is necessary to use an inexpensive solvent. In terms of cost, the above-mentioned combination system of aromatic hydrocarbon and alcohol is preferable because it can be obtained relatively inexpensively.

In this way, the above-mentioned solvent was added to the agent A to reduce the viscosity.
A modified epoxy acrylate is synthesized by charging 1.2 equivalents of methacrylic acid and/or acrylic acid.
The amount of the above-mentioned solvent to be added may be adjusted as appropriate to ensure smooth stirring, and usually 50 to 200 phr is sufficient. Here, I would like to explain the case where the amount of the solvent charged is small. For example, when synthesizing modified epoxy acrylate using a toluene/n-butanol mixed solvent as the solvent, the reaction temperature can be kept high, so the reaction time can be shortened. The corner is convenient. When adjusting the viscosity of the final varnish, it is preferable to incorporate a low boiling point component, such as a toluene/methanol mixed solvent, so that the prepreg can be formed in a short time.

When the modified epoxy acrylate synthesis is carried out in the presence of a mixed solvent as described above, the reaction conditions (temperature, time) vary depending on the boiling point of the solvent used, but it is usually carried out at a temperature of 60 to 110°C. On this occasion,
A polymerization inhibitor and an epoxy ring-opening catalyst are added to carry out the reaction. As the polymerization inhibitor, for example, 0.005 to 0.1% of hydroquinone, monomethoxyhydroquinone, quinhydrin, sulfur, picric acid, etc. may be added. Further, as the catalyst, amines such as benzyldimethylamine and benzyldiethylamine, or quaternary ammonium salts such as triethylbenzylammonium chloride, trimethylbenzylammonium chloride, and triethylbenzylammonium bromide are suitable. It may be added within the range.
The modified epoxy acrylate varnish thus synthesized contains a photosensitizer (for example, benzoin alkyl ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether, and quinones such as anthraquinone and 2-methylanthraquinone). Compound) is blended in an amount of 0.05 to 5% by weight based on the solid content,
Furthermore, it may be diluted with an appropriate mixed solvent in order to improve the workability of impregnating and coating the varnish during prepreg production. In addition, for prepreg production, the varnish is coated with, for example, glass cloth, glass tape, or a surface treatment agent (acrylic silane, epoxy silane, amino silane).
It is applied and impregnated onto chemically treated cloth, non-woven fabric, roving, etc., and the solvent is evaporated in a furnace.

The prepreg thus obtained can be cured by light irradiation, and a cured product with excellent properties can be obtained. As the light source used in this case, those that effectively generate ultraviolet rays can be used, such as a low-pressure mercury lamp, a high-pressure mercury lamp, a xenon lamp, and sunlight. Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Put 95 g of epoxy resin (Ciel Co., Ltd., trade name Epicote-828, molecular weight about 380, epoxy equivalent about 190) into a four-necked flask equipped with a stirring bar, thermometer, gas inlet, and reflux device, and add 100 to 100 g of epoxy resin. Warm to 130℃,
27 g of polyvinyl formal (Chitso Corporation, trade name Vinylec F, type E, molecular weight approximately 43,000) was added in portions and dissolved. Then add the contents to 180-200
The mixture was heated to 0.degree. C. and stirred for 3 hours under a nitrogen gas stream to obtain active product A. Next, reduce the temperature of this content to approximately 90°C.
After gradually adding 169 g of toluene/n-propanol (mixed weight ratio 70/30) as a reaction solvent and homogeneously dissolving it, 0.069 g of hydroquinone and 6.9 g of triethylbenzylammonium chloride (TEBAC) were added, followed by 43 g of methacrylic acid. was added and esterified at a temperature of 85 to 95°C. Modified epoxy acrylate B having an acid value of 8 (based on solid content) was obtained in about 5 hours. The varnish B has a light brown transparent appearance. To this varnish B, benzoin isobutyl ether was added in an amount of 2% by weight based on the solid content, and toluene/methanol (70/30) 111
g to obtain diluted varnish C having a solid content of approximately 37% and a viscosity of 1.3 poise at 25°C. The varnish C was stored in a brown glass bottle and its changes over time were examined, but the properties remained the same as the initial state even after 3 months or more.

Example 2 14g of polyvinyl formal was blended, and erene/n-butanol (mixed weight ratio
Modified epoxy acrylate (B) with an acid value of 6 was obtained in the same manner as in Example 1, except that 92 g of 70/30) and 5.1 g of TEBAC were used. The varnish (B) had a lower degree of coloration than varnish B of Example 1. 1% by weight of benzoin ethyl ether based on the solid content was added to the varnish (B), and benzene/methanol (mixed weight ratio
60/40) to obtain a diluted varnish (C) with a solid content of 45% and a viscosity of 2.6 poise at 25°C. The stability of the varnish was good for more than 3 months.

Example 3 The amount of PVF was 48 g, and toluene/n-butanol (mixed weight ratio 80/20) was used as the reaction solvent.
295g, TEBAC6.9g and esterification temperature 95~
Modified epoxy acrylate (B) was obtained in the same manner as in Example 1 except that the temperature was 105°C. The varnish had a brown transparent appearance. Add benzoin isobutyl ether to this varnish (B) in an amount of 3% by weight based on the solid content.
The mixture was further diluted with 480 g of toluene/ethanol (mixed weight ratio 60/40) to obtain varnish (C). The varnish (C) was a diluted varnish (C) with a solid content of 19% and a viscosity of 0.9 poise at 25°C. Its stability has been maintained for more than 3 months.

Example 4 Epicoat was added to the same four-necked flask as in Example 1.
828 (mentioned above) and 77 g of a phenoxy resin methyl ethyl ketone solution (manufactured by Toto Kasei, solid content 35%) were mixed, and the methyl ethyl ketone was distilled out of the system by increasing the nitrogen flow while increasing the temperature. of
It was kept at 190°C ± 5°C for 3 hours and used as the active substance (A).
Modified epoxy acrylate in the same manner as in Example 1
(B) and further diluted varnish (C). The varnish (C)
It is pale brown and transparent and stable over a long period of time.

Example 5 In a flask similar to Example 1, 60 g of Epicote 828 (mentioned above), 35 g of Epicote-1001 (manufactured by Ciel Chemical, molecular weight approximately 900, epoxy equivalent approximately 480), and
PVF dioxane solution (solid content 14%) 184g, phenoxy resin methyl ethyl ketone solution (previously)
Blend 18 g of the mixture, and while increasing the temperature, nitrogen gas is flowed liberally to distill the solvent out of the system. Next, the contents
After keeping it at 180-200℃ for 3 hours to form the active substance (A), approx.
The temperature was lowered to 90°C, and 185 g of toluene/n-butanol (mixed weight ratio 70/30) was added as a reaction solvent.
After making a homogeneous solution, add 20g of methacrylic acid and acrylic acid.
14g, and hydroquinone 0.07g, TEBAC 6.5g
was charged and esterified at a reaction temperature of 95°C. Approximately 5
Modified epoxy acrylate (B) with an acid value of 9 was obtained in hours. The varnish (B) has a pale brown and transparent appearance. 2% by weight of benzoin isobutyl ether is added to the solid content, and toluene/methanol (70/30) 116 is added as a diluting solvent.
A varnish (C) with a solid content of 34% and a viscosity of 1.2 poise at 25°C was obtained. No change was observed in the varnish (C) even after three months or more.

Example 6 Using each varnish (C) obtained in Examples 1 to 5,
Prepreg was produced. That is, each varnish (C) was placed in a stainless steel dish, a plain-woven glass tape (tape width 3.8 cm, thickness 0.19 mm) was introduced into the dish, and after being impregnated with varnish, the varnish was applied to the tape while being squeezed between rotors. Coated and impregnated. At this time, the ironing pressure was adjusted so that the resin adhesion amount was around 30%. This varnish-impregnated tape was air-dried for about 30 minutes at room temperature, and then the solvent was completely evaporated in a hot air circulating oven at 80°C. The tape thus obtained was a prepreg tape that was not sticky and had a supple appearance, and could be easily wound around articles. The prepreg tape is approximately 10 cm long from an ultraviolet irradiation device (80w/cm, one 2.5kw high-pressure mercury lamp).
When irradiated with light for 3 seconds at the bottom, an excellent cured product was obtained. An alignment tape was also prepared using a roving system as a glass base material, and the prepreg similarly maintained good workability and had excellent photocurability.

Example 7 The varnish obtained in Example 1 was applied to a tin plate, the solvent was evaporated, and then photocured in the same manner as in Example 6. A cured film was produced. The film was tested for the effect of modified epoxy acrylate on evaluation of cross-linking density and amount of solvent extraction.

To measure the cross-linking density, a direct-reading dynamic viscoelasticity measuring device (Toyo Baldwin, Vibron DDV) was used.
) was used to determine the elastic modulus of the rubber-like flat part at high temperatures. As a result, the crosslinked polymer exhibited the characteristics of a highly crosslinked system with a rubber elastic modulus of 7.6×10 ⁸ (dyne/cm ² ).

Solvent extraction uses dioxane, a solvent with high solubility for PVF components, and extracts a 5 cm square film in a Soxhlet extractor at the boiling point of dioxane for 8 hours, and calculates the weight loss of the film. It was less than 1%.

Extracted amount (%) = a-b/a x 100 a: initial weight b: weight of film dried after extraction As described above, in the modified epoxy acrylate of the present invention, the linear polymer and prepolymer are It is believed that physical and physical bonds are introduced, and the system as a whole forms a densely cross-linked polymer.

Reference Example 1 A blend varnish was synthesized as follows. In a flask similar to Example 1, 150 g of Epicote 828, 68 g of methacrylic acid, and 0.2 g of hydroquinone,
Add 1.1 g of TEBAC and heat and stir at 100 to 130°C for 3 hours to synthesize epoxy acrylate with an acid value of 10. Next, 264g of toluene/methanol (70/30)
After adding and dissolving uniformly, add 43g of PVF,
Dissolve uniformly. Next, benzoin isobutyl ether was added in an amount of 3% by weight based on the solid content to prepare a blend varnish. This varnish is light brown and transparent with a solid content.
49%, and the viscosity at room temperature was 7.6 poise. This varnish began to become slightly cloudy after about 14 days, and then gradually became cloudy, and after about one month, the varnish appeared to be in a gelled state due to the precipitation of PVF. About this prepreg varnish,
A cured film was prepared in the same manner as in Example 7, and the crosslinking density and extraction amount were tested. The value of the rubber elastic modulus was 3.2×10 ⁸ (dyne/cm ² ). This value is about 1/2.3 of the cured product system of Example 1. On the other hand, regarding the amount of extraction, about 4% was observed.

In the case of a blend varnish, there is no modification effect as in the present invention, so no modification intended to introduce affinity between compositions and physical and chemical bonds as described above has been introduced. This is considered to be the reason for the lack of stability as a varnish and the simultaneous deterioration of the properties of the cured product.

Comparative Example 1 When dioxane, tetrahydrofuran, and methyl ethyl ketone were added as diluents to the modified epoxy acrylate varnishes (B) obtained in Examples 1 to 3, either alone or as a mixture, they became cloudy and gelled within 0 to 8 hours. I got into a state.

Claims (1)

[Claims] 1. An epoxy resin containing 10 to 40 phr of polyvinyl formal or/and phenoxy resin.
After reacting at a temperature of 150 to 230°C, in the presence of a solvent, 0.7 to 1.2 equivalents of (meth)acrylic acid per 1 epoxy equivalent, a small amount of polymerization inhibitor, and an epoxy ring-opening catalyst are blended to increase the acid value. 1. A method for producing a photocurable prepreg tape varnish, which is characterized by reacting the varnish to 10% or less and blending 0.05 to 5% by weight of photosensitized varnish. 2. The method for producing a varnish according to claim 1, wherein the solvent is a mixture of 80 to 60 parts by weight of aromatic hydrocarbon and 20 to 40 parts by weight of alcohol.