JPS5843513B2 - sizing size - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sizing agent for carbon fibers.

More specifically, the present invention relates to a sizing agent for carbon fibers that facilitates handling of carbon fibers and improves composite physical properties thereof.

Carbon fiber is lightweight, has high strength, and has high modulus5.
In recent years, it has attracted attention as a reinforcing material for composites due to its low price.

Since carbon fibers are brittle fibers with low elongation, mechanical friction easily causes single filaments to break, resulting in so-called fuzz.

Such fuzz is generated during cloth weaving, prepreg manufacturing,
Occurs during filament winding molding, etc.
This not only causes a significant decrease in workability, but also causes a decrease in the physical properties of the composite.

Conventionally, in order to facilitate the handling of carbon fibers, sizing has been carried out using a composition containing bisphenol A/digrindyl ether type epoxy resin as the main component.
These sizing agents are unable to impart sufficient binding force to carbon fibers, and as a result, fuzz occurs during cloth weaving, prepreg manufacturing, filament winding molding, etc., resulting in a decrease in workability. There was a problem.

On the other hand, carbon fibers inherently have a low affinity with matrix resins, so when made into a composite, although the tensile strength reflects the properties of the fibers and exhibits high strength, for example, the interlaminar shear strength (Inter Lam)
1nar 5hear Strength), there is a serious defect that sufficient characteristics cannot be obtained.

As a means to improve the compatibility between the carbon fiber and matrix resin and to improve the interlaminar shear strength when making a composite, the surface of the carbon fiber is oxidized in the gas phase or liquid phase, and carboxyl groups and phenolic hydroxyl groups are added to the surface of the carbon fiber. A method of introducing a functional group is commonly used.

This surface oxidation treatment must also be carried out within a range that does not impair the tensile strength of the carbon fiber itself, and naturally has its limits.

However, although this surface oxidation treatment improves the adhesion between the fibers and the matrix and thus improves the interlaminar shear strength of the composite, it is much lower than the required level, which may lead to poor reliability, for example. In the important application fields of carbon fiber reinforced composite materials, it is strongly desired to improve the interlaminar shear strength by improving the surface properties of carbon fibers.

In the end, the conventional surface treatment method for carbon fiber is
The main point of this method is to perform surface oxidation treatment in the gas phase or liquid phase, and then sizing it with a composition containing bisphenol A/diglycidyl ether type epoxy resin as the main component. If the handleability is sufficiently improved and the material is made into a composite, it is not possible to obtain high interlaminar shear strength.

In this way, in the conventional method, the aforementioned epoxy resin is used as the main component of the sizing agent, but this is because epoxy resin is often used as a matrix when manufacturing carbon fiber reinforced composite materials. Therefore, it is thought that using a sizing agent with the same chemical structure as the matrix eliminates the problem of compatibility between the sizing agent layer/matrix interface and minimizes the decrease in interlaminar shear strength due to sizing. It will be done.

The present inventors have developed a new sizing agent that can overcome the drawbacks of conventional sizing agents for carbon fibers as described above, greatly improve the handling of carbon fibers, and improve the interlaminar shear strength of composites. As a result of intensive research aimed at developing the invention, it was discovered that the objective could be achieved by using a solution or emulsion of a vinyl addition polymer having an oxirane ring in the side chain.Based on this knowledge, the present invention was made. It's arrived.

The reason why the sizing agent according to the present invention can impart excellent handling properties to carbon fibers is thought to be due to the binding power of the vinyl addition polymer.

Conventionally used condensation resins such as epoxy resins do not have such high binding strength.

On the other hand, the sizing agent according to the present invention imparts excellent surface properties to carbon fibers, and as a result, when composited, the oxirane ring of the side chain of the vinyl addition polymer exhibits high interlaminar shear strength. This is thought to be because it reacts relatively easily with functional groups such as carboxyl groups on the fiber surface, and at the same time reacts with the oxirane ring of the epoxy resin of the matrix.

In this case, what is important is that the oxirane ring-containing vinyl addition polymer contained in the sizing agent composition according to the present invention,
With the conventionally used bisphenol A/diglycidyl ether type epoxy resin, the distribution of chemical bonds at the sizing agent/carbon fiber interface and the sizing agent/Mad IJ Tsux interface, the effective length of the chemical bond, and the reacted interfacial molecules The rotational degree of freedom, the rigidity of the interface layer, etc. are slightly different.
This means that

Of course, these properties and structures depend on the composition of the sizing agent composition according to the present invention, particularly on the chemical composition of the vinyl addition polymer having an oxirane ring in the side chain, and the oxirane ring size depends on the sizing agent composition according to the purpose specifications of the sizing. It is important to carry out molecular design of vinyl-based addition polymers.

For example, sizing carbon fibers with a composition based on an oxirane ring-containing vinyl addition polymer that forms a relatively flexible interfacial layer increases the interfacial elasticity between the carbon fibers and the matrix when composited. , the additional effect of mechanically improving the impact absorption capacity and, as a result, improving the impact resistance of the composite is also obtained.

As described above, the sizing agent composition according to the present invention can provide extremely excellent handling properties to carbon fibers, and at the same time can greatly improve the physical properties of the composite, especially the interlaminar shear strength, and can improve the properties of carbon fiber reinforced composite materials. It has extremely important significance for development.

The sizing agent according to the present invention has a vinyl addition polymer having an oxirane ring in the side chain as a main component, and if necessary,
It is a solution or emulsion containing additives such as lubricants, softeners, and film-forming aids.

Among these, the vinyl addition polymers having an oxirane ring in the side chain used in the present invention include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, α-ethyl glycidyl acrylate, crotonyl glycidyl ether, glycidyl crotonate, glycidyl Incrotonate, monoalkyl itaconate monoglycidyl ester, diglycidyl itaconate, monoalkyl nistermotricidyl fumarate, diclycidyl fumarate, monoalkyl nistermotricidyl maleate, diglycidyl maleate A vinyl addition polymer or/and any vinyl addition polymer obtained by polymerizing one or more oxirane ring-containing ethylenically unsaturated compounds selected from esters etc. alone or together with other monomers, It refers to one type or a mixture of two or more types of polymers into which an oxirane ring is introduced as a side chain segment component by graft polymerization or other means.

These vinyl addition polymers having an oxirane ring in their side chains include methyl methacrylate, ethyl methacrylate,
Alkyl methacrylates such as butyl meccrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate,
Alkyl acrylates such as lauryl acrylate, styrene derivatives such as styrene, α-methylstyrene, and vinyltoluene, fatty acid vinyl esters such as vinyl acetate and vinyl propionate, unsaturated hydrocarbons such as butadiene and isoprene, vinyl chloride, chloroprene, etc.・Rogenated unsaturated hydrocarbons, unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, vinyl acetic acid, α-ethyl acrylic acid, angelic acid,
Unsaturated fatty acids such as monomethyl ester, monoethyl ester, monobutyl ester of itaconic acid, maleic acid or fumaric acid, maleic anhydride, itaconic anhydride, etc.
-Hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, 2-chloro-3-hydroxypropyl methacrylate, phosphoric acid mono(hydroxypropyl methacrylate) ester, acrylamide, methacrylamide, N-methylolacrylamide, N-methoxymethylacrylamide, N- 1 selected from ethylenically unsaturated compounds such as butoxymethylacrylamide
in combination or without combination with a species or more than one monomer,
It is produced by solution polymerization, emulsion polymerization, or suspension polymerization of one or more monomers selected from the above-mentioned oxirane ring-containing ethylenically unsaturated compounds in a conventional manner.

In this copolymerization reaction, ketone,
Esters, alcohols, ethers, aromatic hydrocarbons, etc. can be used, and as a dispersion medium in the case of heterogeneous polymerization, water or a mixture of water and a water-soluble organic solvent can be used.

Further, as the polymerization initiator, peroxides, azo compounds, etc. can be used.

Furthermore, a chain transfer agent such as a mercaptan can also be used if necessary.

By graft polymerization to any vinyl addition polymer,
The case where an oxirane ring is introduced as a side chain segment component is also similar to the case of the above-mentioned copolymerization.

Among the vinyl addition polymers having an oxirane ring in the side chain used in the present invention, the glass transition temperature is 110° to 60°.
°C, its solubility parameter is 8,8 (Cal/c
c) A polymer of 3A or more, the content of oxirane group-containing monomer units is 5 mol% or more, and the intrinsic viscosity at 25°C is, for example, 0.04 d in a methyl ethyl ketone solution.
A polymer having a ratio of 1/f or more is particularly effective in achieving the desired effects of the present invention.

However, it is not necessary to satisfy all of these conditions (also,
Since the effects of the present invention can be obtained in many cases, the scope of the present invention is not limited to the above-mentioned composition range.

In carrying out the present invention, the intrinsic viscosity of the vinyl addition polymer having an oxirane ring in the side chain depends on the film-forming ability of the sizing agent and the toughness of the film, and the glass transition temperature depends on the flexibility of the film. Solubility parameters are determined by intermolecular cohesive force (film toughness) and affinity with fibers, and the content and form of oxirane ring-containing structural units are determined by the chemistry formed at the fiber/sizing agent/matrix interface. Since the number of bonds and interfacial elasticity are closely related, it is important to design the molecule according to the intended sizing specifications.

On the other hand, as lubricants that can be included in the sizing agent composition according to the present invention as necessary, stearic acid, stearate esters, nonionic and/or anionic surfactants, silicone resins, etc. can be used. .

However, the use of a large amount of silicone-based resin must be avoided because it will reduce the affinity between the fibers and the matrix resin when forming a composite.

The weight ratio of these lubricants to the sizing agent composition is
It is preferably 40% or less.

Examples of the softening agent that can be added to the sizing agent according to the present invention as desired include nonionic and/or anionic surfactants, polyethylene glycol, and the like.

Film-forming aids that can be added to the sizing agent according to the present invention as desired include plasticizers such as dibutyl phthalate and dioctyl phthalate, various organic solvents, and water.

The sizing of carbon fibers with the sizing agent according to the present invention involves impregnating the carbon fibers with a dispersion of the sizing agent according to the present invention, such as an organic solvent solution, an aqueous solution, or an emulsion, and then removing the solvent or dispersion medium by drying. It is usually done in this way.

The active ingredient concentration of these solutions or emulsions is 2
The content is preferably 5% or less, particularly preferably in the range of 0.5 to 5%.

Depending on the composition of the sizing agent and the chemical structure of each component, solvents for solutions include ketones, esters, ethers,
Alcohols, hydrocarbons, etc. can be used.

When sizing carbon fibers using the sizing agent of the present invention, the amount of the active ingredient attached to the carbon fibers is 0.
．． The concentration of the active ingredients in the sizing bath, the impregnation time or impregnation rate, the tension of the carbon fiber during impregnation, and the sizing bath so that the active ingredients are within the range of 2 to 5% and uniformly adhere to the carbon fiber surface. It is preferable to control the temperature etc.

The sized carbon fibers are dried using an infrared lamp, hot air, etc. at a time and temperature depending on the solvent or dispersion medium to remove volatile components.

When sizing carbon fibers using the sizing agent of the present invention, the first component, for example, a vinyl addition polymer having an oxirane ring in the side chain, is first sized by the method described above, and then the second component is sized. , for example, by sizing polyethylene glycol.

Carbon fibers to which the carbon fiber sizing agent of the present invention is applied include carbon fibers, graphite fibers, carbonaceous or graphite fibers such as graphite whiskers, or needle-like single crystals, and mats and fabrics mainly composed of them. Examples include braiding, and the above-mentioned fibers or whisker-like single crystals surface-activated by oxidation treatment or other methods are particularly preferred.

In order to describe the invention in more detail, specific examples are given below, but these examples are not intended to limit the invention in any way.

Example 1 150 g of ethyl acetate as a reaction solvent was placed in a 500 ml fourth flask equipped with a stirrer, reflux condenser, dropping funnel, and thermometer, and heated to 75° C. while purging with nitrogen.

Into the dropping funnel were 55f of methyl methacrylate, 351 butyl acrylate, 10f of glycidyl methacrylate, and 0.3f of N-N'-azobisisobutyronitrile as a polymerization catalyst. The reaction was completed by adding the mixture dropwise into the flask over 2.5 hours and then heating to 75° C. for 5.5 hours.

The polymerization rate of the obtained copolymer was 96%.

Next, the obtained polymer solution 50S' was collected and 95%
0i of ethyl acetate was added to prepare a sizing agent solution with a concentration of about 2%.

Next, using a bobbin sizer, carbon fiber Carboron Z2-1 manufactured by Nippon Carbon ■ (registered trademark, intermediate product with only surface oxidation treatment and no sizing) was heated at 5 rIL/min in the sizing agent solution. The solution was passed through Carboron Z-2-1 continuously at a speed of , sizing was applied.

The amount of active ingredient in the sizing agent attached to the carbon fibers was 1.6% based on the carbon fibers.

Next, the binding force of the obtained carbon fibers was measured using a TM yarn friction binding force tester.

The ranking of conjugation power was performed according to the following criteria.

A: Only singular fuzz is generated.

B: Multiple fluffs are generated.

C: Fuzz occurs in clusters.

D: Fuzz occurs all over the surface.

The obtained results are shown in Table 1 and Table 2 together with Comparative Example 1.
Shown in the table.

Separately, carbon fibers subjected to the above-mentioned sizing treatment were mixed with epoxy resin Epicoat 828 (registered trademark) 90-OS' manufactured by Shell Co., Ltd., boron trifluoride monoethylamine 3
61. Carbon fibers that are continuously impregnated with a resin solution consisting of methyl ethyl ketone 1001 and that retains the resin solution are wound in parallel around a drum winder.
A unidirectional carbon fiber prepreg was created by heating at 30° C. for 20 minutes to partially cure the resin layer.

13 sheets of the obtained prepreg were stacked in the same direction at 170°.
Heat and pressurize at C17kg/crA for 3 hours, and then
A unidirectionally reinforced carbon fiber composite material (hereinafter abbreviated as CFRP) was produced by heating at 70° C. and normal pressure for 2 hours.

The carbon fiber content of the obtained CFRP was 58 Vol-%.

Next, the interlaminar shear strength of the obtained CFRP was measured according to the method specified in ASTM-D2344.

All test pieces had two thicknesses. The results obtained,
It is shown in Tables 1 and 2 together with Comparative Example 7r.

Comparative Example 1 Instead of the methyl nucleate/butyl acrylate/glycidyl methacrylate copolymer in Example 1,
Using a 4:1 mixture of epoxy resin Epicoat 1004 (registered trademark) manufactured by Shell Co., Ltd. and Epicoat 828 (registered trademark) thereof, carbon fiber Carbon fiber Carbon Z-2-1 manufactured by Nippon Carbon ■ was prepared in the same manner as in Example 1. (registered trademark, an intermediate product that has undergone only surface oxidation treatment and no sizing at all) was subjected to sizing treatment.

The amount of the active ingredient of the sizing agent attached to the carbon fiber is 1.
It was 6%.

Next, in the same manner as in Example 1, the binding force of the sized carbon fibers and the interlaminar shear strength of the composite were measured.

The carbon fiber content of the CFRP test piece used for this measurement was
58Vo1%.

The obtained results are shown in Tables 1 and 2 together with Example 1.

Further, as a blank test, the binding force and interlaminar shear strength of the composite were similarly measured for unsized Carboron Z-2-1 [F] (registered trademark) which was not subjected to any sizing.

The carbon fiber content of the CFRP test piece used for this measurement was
The same <58 Vol-%.

The results obtained are shown in Tables 1 and 2.

Example 2 Carbon fiber Carbon Z-2 manufactured by Nippon Carbon ■ of Example 1
All procedures were carried out in the same manner as in Example 1, except that carbon fiber Magnamai HT-8 (registered trademark, surface oxidation treatment was applied, but no sizing was performed at all) manufactured by Percules Co., Ltd. was used in place of -1■. Then, the carbon fibers were sized, and the interlaminar shear strength of the composite was measured for the obtained carbon fibers.

The carbon fiber content of the CFRP used for this measurement was 55Vo.
It was l-%.

The obtained results are shown in Table 3 together with Comparative Example 2.

Comparative Example 2 Carbon fiber Carbon Z-2 manufactured by Nippon Carbon ■ in Comparative Example 1
-1 [F] instead of Magnamai) H manufactured by Percules
Carbon fibers were sized in the same manner as in Comparative Example 1 except that T-8 (registered trademark) was used, and the interlaminar shear strength of the composite was measured for the obtained carbon fibers.

The carbon fiber content of the CFRP test piece used for this measurement was 5
It was 5Vo1-%.

The results obtained are shown in Table 3 together with Example 2.

Further, as a blank test, the interlaminar shear strength of the composite was similarly measured for unsized Magnamite HT-3 which was not subjected to any sizing.

The carbon fiber content of the CFRP test piece used for this measurement was 5
It was 5 Vol-%.

The results obtained are shown in Table 3.

Examples 3 to 7 Carboron Z manufactured by Nippon Carbon ■ was prepared in the same manner as in Example 1 except that the composition shown in Table 4 was used instead of the methyl methacrylate/butyl acrylate/glycidyl methacrylate copolymer in Example 1. -2-1 (registered trademark) was sized, and the binding force and interlaminar shear strength of the composite were measured for the obtained carbon fibers.

The amount of the active ingredient of the sizing agent adhered to the carbon fibers was 1.5 to 1.7% in all cases.

Further, the carbon fiber content of the CFRPs subjected to this measurement was all 58 to 60 Vol-%.

The obtained results are shown in Table 4 together with Comparative Examples 3 and 4.

Comparative Examples 3 to 4 Shell Co., Ltd. epoxy resin top (Picot) 1 in Comparative Example 1
004 (registered trademark) and Epicote 828 (registered trademark)
Carboron 2-2-1 [F] (registered trademark) manufactured by Nippon Carbon ■ was prepared in the same manner as in Comparative Example **1, except that the composition shown in Table 4 was used instead of the 4:1 mixture of After sizing, the binding force and interlaminar shear strength of the composite were measured for the carbon fibers obtained.

The amount of the active ingredient of the sizing agent adhered to the carbon fibers was 1.5 to 1.7% in all cases.

Further, the carbon fiber content of the CFRPs subjected to this measurement was all 58 to 60 Vol-%.

The results obtained are shown in Table 4 together with Examples 3 to 7.

Claims (1)

[Claims] 1. If desired, at least one auxiliary component selected from lubricants, softeners, and film-forming aids is added to a solution or emulsion of a vinyl addition polymer having an oxirane ring in the side chain. A sizing agent for carbon fiber.