JPS6022012B2 - prepreg sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a prepreg sheet, and in particular, an object of the present invention is to provide a novel prepreg sheet that has excellent adhesiveness and heat resistance, is quick-curing, and has excellent storage stability. It is something.

Conventionally, post-adhesives for impregnating prepreg sheets used in fields requiring heat resistance include epoxy resins, polybenzimidazole resins, and polyimide resins.

However, conventional epoxy resins have insufficient heat resistance and adhesive properties at high temperatures such as 150 to 200°C, and polybenzimidazole resins and polyimide resins generally have poor adhesive properties and are used at high temperatures during bonding work. The problem is that the range of use is limited because it requires , and it is expensive. The properties required for adhesives, especially high-temperature resistance properties, are becoming stricter year by year, and there is a demand for the development of new adhesives that can meet these requirements.Recently, polyvinylphenol used in epoxy resins has been developed as a material that improves heat-resistant properties. Although curing agents have been developed, they still have problems with storage stability, which limits their use.

As a result of intensive research to solve the above problems, the inventors of the present invention succeeded in developing a new prepreg sheet with excellent heat resistance and high temperature adhesion. It was found that it had a remarkable effect of having excellent storage stability.

A feature of the present invention is that by substantially covering all or most of the surface of the curing accelerator with epoxy resin, reaction with the curing agent in the mixed system is avoided, and a prepreg sheet with good storage stability is obtained. In particular, for this purpose, a component containing a curing agent and a component containing a curing accelerator are prepared separately to form two components.

That is, the gist of the present invention is to provide a first component mainly composed of an epoxy resin and a polyvinylphenol curing agent;
a second component comprising a curing accelerator fractionally mixed into the component;
and a support base material that supports both of these components, and the second component is made by dispersing and mixing the curing accelerator in an epoxy resin of the same kind or a different kind as the first component epoxy resin, and then powdering the mixture. The prepreg sheet is characterized by:

Here, the first component consists of a normal epoxy resin and its curing agent, a polyvinylphenol compound, such as polyparavinylphenol or its bromide, and these are mixed in a normal heating and mixing device at a temperature at which no curing reaction occurs. It is prepared by uniformly mixing under certain conditions and letting the phases fall out, and this is cooled and crushed to form a powder, or used as it is in a sticky semi-solid form.

The mixing ratio of the first component epoxy resin and the polyvinylphenol curing agent is appropriately such that the epoxy group/OH group equivalent ratio is 0.5 to 3, taking into consideration the amount of epoxy resin in the second component described below. In particular, a ratio of 0.8 to 2 gives good results in terms of heat resistance and adhesiveness.

If necessary, inorganic fillers such as talc, silica, and calcium carbonate, various pigments, and metal powders such as iron and aluminum may be added. The first component prepared in this way is storage stable, with almost no reaction between the epoxy resin and the curing agent occurring under normal storage conditions unless a curing accelerator such as an organic amine is added. It has sex.

The second component uses an epoxy resin of the same type or different type as the epoxy resin in the first component, and a curing accelerator for the first component is added to this, particularly preferably dicyandiamide, diaminodiphenylsulfon, or modified products thereof (however, Modified products include derivatives of these or mixtures of these with additives such as imidazole), either alone or in combination, to make them compatible by uniformly mixing them in a normal heating mixing device at a temperature that does not cause a curing reaction. This is usually 35
It is prepared by pulverizing the powder to a particle size of less than 1,000 square meters, preferably 14 square meters or less.

By reducing the particle size in this way, good results can be achieved in uniform dispersion in the first component. In the second component containing the curing accelerator powderized as described above, all or most of the surface of the curing accelerator is substantially covered with the epoxy resin.

In order to ensure this state, the amount of the epoxy resin used is preferably 1 to 5 times the amount of the curing accelerator. At this time, if the amount of epoxy resin is less than the same amount as the amount of curing accelerator, the surface coating with the epoxy resin will be insufficient, and therefore the storage stability of the adhesive obtained by mixing the first component and the second component will deteriorate. This results in an extremely low value, which defeats the purpose of the present invention. On the other hand, if the amount is more than 5 times the amount, the amount of the second component epoxy resin in the composition becomes too large, which is undesirable because the heat resistance or adhesiveness of the cured product will be impaired. In preparing the powdered second component in this way, an imidazole compound or a tetraalkyl compound may be added as necessary for the purpose of accelerating the curing of the epoxy resin contained in the second component rather than as a curing accelerator for the first component. A curing accelerator such as guanidine may be added.

The second component thus prepared does not undergo any reaction between the epoxy resin and the curing accelerator under normal storage conditions and is itself storage stable.

The epoxy resin used for the above first and second components is 1
Any material having two or more epoxy groups in the molecule can be used, such as diglycidyl epoxy resins, cycloaliphatic epoxy resins, novolac epoxy resins, triglycidyl isocyanurate, halogenated epoxy resins, etc. , these can be used alone or in combination.

As described above, the epoxy resin for the second component is the same or different from the epoxy resin for the first component. In order to avoid diffusion and migration into the interior as much as possible, it is preferable to use a material that is solid at room temperature and has a softening point of 70° C. or higher. Next, the first component and second component prepared as described above are applied to a supporting substrate such as cloth such as glass fiber, polyamideimide fiber, or polyester fiber, or nonwoven fabric, or metal foil such as aluminum, copper, or stainless steel. Spread it on the surface of the material, then extrude and mix to make a prepreg sheet.

That is, in general, if the first component and the second component are both powders, the powders are mixed using a V-type blender or the like to obtain a uniformly mixed and dispersed adhesive. In this case, the powder of the second component is in an unmolten state, or even if it is melted, it is melt-mixed with a hot roll or the like at a temperature that maintains the above-mentioned coating state so that the second component is uniformly mixed into the first component. The adhesive is dispersed and mixed. next,
Each of the above adhesives is uniformly spread onto a supporting base material, and heated using heating means such as far infrared heating and high frequency heating to ensure that the second component, the curing accelerator, is completely or almost unmolten. A prepreg sheet can be obtained by heat-sealing the prepreg sheet to a supporting substrate under conditions such that the entire surface or most of the surface remains coated with the epoxy resin.

Alternatively, a prepreg sheet can also be obtained by first applying one component onto a supporting base material, heat-sealing this, and then applying and heat-sealing the other component thereon.

In this case, it is usually preferable to apply the second component and then apply the first component, and conversely, when applying the second component after adhering the first component, the melting point of the resin of the second component is usually Since the resin is high, there is a risk that the first component resin will melt and the coating state of the second component curing accelerator will be damaged, resulting in a decrease in storage stability as a prepreg sheet. The appropriate mixing ratio of both components is such that the curing accelerator in the second component is 1 to 1 part by weight relative to the total weight of 10 parts by weight of the cepoxy resin and curing agent in the first component. Particularly preferred is 3 to 6 parts by weight. When the curing accelerator is less than 1 part by weight based on the cloud weight of 10 resin in the first component, the resulting prepreg sheet has a slow curing speed during use, and there is a risk that some areas may be insufficiently cured. When the amount is more than 2 parts by weight, a large amount of eboxy resin in the second component is required, and the heat resistance properties of the resulting prepreg sheet tend to deteriorate. The Bripreg sheet of the present invention obtained as described above has a barrier film of epoxy resin between the curing agent in the first component and the curing accelerator in the second component in the mixed system. In particular, it has extremely excellent storage stability; for example, under normal storage conditions of 4000°C, the hardening agent and hardening accelerator will harden within a week, but it can be stored for about one month or more. It is possible, and moreover, when this prepreg sheet is applied to an article to be bonded and cured by heating under specified conditions, it maintains 75 to 85% of the adhesive strength at room temperature even at a high temperature of 200 oo, and has fast curing properties. It has remarkable effects and can be used as a structural adhesive for high-temperature applications.

The present invention will be specifically explained below using Examples.

In the examples, all parts indicate parts by weight. Example 1 Bisphenol type epoxy resin (Shell Chemical Co., Ltd. product "Epicote 828"; average eboxy equivalent 184 to 1 child), cresol noporac type epoxy resin (Nippon Kayaku ■
Product rEOCNI02J: average epoxy equivalent weight 215-2
35) 66 parts, polyparavinylphenol (Maruzen Sekiyu ■
Product “Resin M”: Hydroxyl equivalent: approx. 120) Shibe: 110
The mixture was mixed and melted in a heated mixing pot at ~120 qo for 3 minutes.

The eboxy group/hydroxyl group equivalent ratio of this formulation is 1.5.
To this, add talc (asakura powder ■ product "S talc JIO base part"), mix at about 120 qo for 30 minutes, cool it, grind it in a pulverizer to make a powder of 60-300 mesh (46-25 qo), and mix this with the first component. Separately, cresol novolak-type epoxy resin (Japan Yihanyaku ■ product ``EOCNI04''
: Average epoxy equivalent: 225-245) Add 10 parts of dicyandiamide and 5 parts of dicyandiamide, mix and disperse in a heated mixing pot of 12 mm, and after cooling, put in a pulverizer to
A powder of ~300 mesh (46 to 14 sand) was prepared, and this was used as the second component.

Next, add 10 parts of the first component to 6 parts of the second component. $ part was added and dry blended for 1 hour at room temperature in a V-type blender. In the resulting adhesive, most of the surface of the curing accelerator (4 parts per 100 parts of the total resin content of the epoxy resin and curing agent in the first component) is covered by the epoxy resin in the second component. It was in a state of being uniformly dispersed in the first component. Next, the above dry blend powder was sprinkled on one side of a glass cloth (Nitto Boseki product "WEI 104") at a ratio of 150 to 200%, and this was fused to the cloth using a far infrared ray device, and then the powder was fused with a press roll. A prepreg sheet A was produced by pressure bonding.

Example 2 100 parts of Epiquat 828 (previous generation) and 64 parts of Resin M (previous generation polyparavinylphenol) were added to 1
The mixture was mixed and melted in a 10oo heated mixing pot.

The epoxy group/hydroxyl group equivalent ratio of this formulation is 1/1.
5 parts of S talc (previous life) were added to this and mixed at 110 oo to obtain a semi-solid first component. The total mixing time above was 60 minutes. Separately, the average epoxy equivalent is 9
50 parts of dicyandiamide to 100 parts of 00 to 1000 epoxy resin (Shell Chemical Co., Ltd. product "Epicote 1004")
186 parts, mixed and dispersed in a 12030 heated mixing pot for 186 minutes, cooled, and then passed through a grinder to a
A mesh powder was prepared, and this was used as the second component.

The second component was added to the first component at a ratio of 5 parts of the curing accelerator in the second component to 10 parts of the total resin content of the epoxy resin and curing agent in the first component. The mixture was mixed with a roll to form a semi-solid adhesive.

Next, this adhesive was extruded and cast onto one side of the same glass cloth as in Example 1 at a temperature of 50 to 6,000 using an extruder to obtain a prepreg sheet B with a resin adhesion amount of 200 kg/m.
was created. Example 3 The first component was exactly the same as that prepared in Example 2, but the second component was prepared in the following manner.

That is, 10 parts of Epicort 1004 (previously) and 50 parts of this diaminodiphenylsulfon were added, mixed and dispersed for 18 minutes in a heating mixing pot at 120°C, and after cooling, the mixture was milled to form a powder of 100 to 300 mesh. This was used as the second component. Next, polyamideimide nonwoven fabric (
First, the above-mentioned second component was sprayed onto one side of Nippon Vilene (product "KH-300$T"), and this was thermally fused to the nonwoven fabric using a far-infrared heating device.

The amount of resin deposited was about 15 days/day. Afterwards,
The above first component was added onto this resin using an extruder at a temperature of 60°C.
The prepreg sheet C was obtained by extrusion and casting at zero temperature.
Incidentally, the amount of the first component deposited was about 100 μm/m as a resin component (excluding filler). In each of the prepreg sheets A, B, and C according to Examples 1 to 3 above, the resin is relatively evenly distributed in the glass cloth or nonwoven fabric, and the
Most of the component resins were dispersed in an unmolten state.

For the above three types of prepreg sheets, a mild steel plate was used as an adherend in a dryer at a temperature of 150°C and an extrusion force of 500 to 1000.
After curing under dry/ground conditions, the tensile strength was measured in an atmosphere of 20° C., 150° C., and 20 pm based on JIS K6850. In addition, the storage stability and gelation time at 150°C of each prepreg sheet were observed. The results were as shown in the table below. As is clear from the above table, the prepreg sheet of the present invention has high adhesive strength even at a high temperature of 20,000 ml, has excellent storage stability, and is far-curable.

Claims (1)

[Claims] 1 A first component containing an epoxy resin and a polyvinylphenol curing agent as main components, a second component containing a curing accelerator dispersed and mixed in this first component, and a supporting base material that supports both of the above components. A prepreg sheet characterized in that the second component is obtained by dispersing and mixing the curing accelerator in an epoxy resin of the same type or different type as the epoxy resin of the first component and pulverizing the mixture.