JPS583501B2 - Carbon fiber reinforced thermoplastic resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-strength, high-rigidity thermoplastic resin composition reinforced with carbon fibers.

Polybunalene terephthalate (hereinafter abbreviated as PBT), a type of thermoplastic polyester, has low water absorption and excellent properties such as mechanical properties, thermal properties, electrical properties, and chemical resistance. It is also attracting attention in the field of molding materials as a resin with performance that is as good as, if not better than, nylon.

When this PBT is reinforced with glass fiber, its mechanical strength and heat resistance are dramatically improved, and it becomes a high-performance material that can replace metals such as sheet metal and die casting.

Similarly, reinforcing PBT with carbon fiber not only produces the same effects as glass fiber, but also has excellent properties such as significantly improved wear properties, increased thermal conductivity, reduced chargeability, and increased electrical conductivity. It is known that it exhibits similar properties, and attempts are being made to develop its application to sliding parts and electrical parts.

When reinforcing PBT with glass fibers, it is common practice to use a silane compound to chemically bond the PBT and glass fibers to improve the reinforcing effect and to achieve practical strength.

However, in the case of PBT and carbon fiber, no effective compound has been found as in the case of glass fiber, since carbon fiber is inert.

Therefore, in order to increase the strength of the PBT-carbon fiber composition, it is necessary to use considerably long carbon fibers, but in this case, this may lead to non-uniform dispersion of the carbon fibers and poor appearance of the molded product. .

Also, the tensile modulus of glass fiber is 7 x 105Kg/cm2
Compared to that, high-rigidity type carbon fiber is 23×10
5kg/cm2, which is about three times larger, so it is expected that carbon fiber-reinforced PBT would have a sufficiently higher elastic modulus than glass fiber-reinforced PBT, but unfortunately, it generally shows the same value. Not too much.

As a result of intensive research, the present inventors surprisingly found that PBT
If carbon fibers treated with a reaction product of a specific PBT with an intrinsic viscosity of 0.2 to 0.6 and hydroxyl groups at both ends and a polyfunctional incyanate and an epoxy resin are used instead of It has been found that even though the length is relatively short, the composition has extremely high values for both strength and elastic modulus, and other properties are comparable.

The reason for this is that the reaction product of PBT (hereinafter abbreviated as L-PBT), which has an intrinsic viscosity of 0.2 to 0.6 and has hydroxyl groups at both ends (hereinafter referred to as L-PBT), and a polyfunctional incyanate (results in a PBT-based polyurethane). It is thought that the strength and elastic modulus of the composition are significantly improved due to the high physical adhesion to the carbon fibers treated with the epoxy resin.

Furthermore, since the L-PBT used in the present invention has a relatively high molecular weight and the amount of polyfunctional incyanate used is relatively small, no deterioration in physical properties due to urethane bonds was found.

Furthermore, the presence of a small amount of epoxy resin is effective in improving strength and elastic modulus, and this is because epoxy resin has excellent adhesion to carbon fibers, but the epoxy group reacts with urethane and incyanate groups, resulting in chemical It is inferred that this is also due to the formation of physical bonds.

Now, the L-PBT of the present invention is obtained by condensing terephthalic acid or an alkyl ester of terephthalic acid (an alkyl group having 1 to 4 carbon atoms) with 1,4-butanediol, and has active hydrogen atoms, especially hydroxyl groups, at both ends. Those having active hydrogen atoms are used.

L-PBT used in the present invention has an intrinsic viscosity [η] of 0.
2 to 0.6; Hydroxyl value (KO equivalent to 1 g of sample hydroxyl group)
Those in which the number of H's is 9 to 37, preferably 11 to 28 are suitable.

It is preferable that both terminals of this L-PBT are all hydroxyl groups, but there is no problem even if some carboxyl groups generated depending on the synthesis conditions are included.

In this case, L-PBT has an acid value (number of KOH reacting with carboxyl groups in 1 g of sample) of 10 or less, and desirably 1/3 or less of the hydroxyl value.

If the intrinsic viscosity of L-PBT used in the present invention becomes too small, the number of urethane bonds in the polyurethane produced will increase, resulting in poor heat resistance; conversely, if the inherent viscosity becomes too large, polyfunctional inorganic This is undesirable because the reaction with cyanate does not proceed uniformly and the adhesion to carbon fibers is poor.

Furthermore, it is also possible to use a copolymer mainly composed of PBT, in which less than 50 of the acid components and alcohol components constituting the L-PBT are replaced with other copolymerizable components.

Copolymerizable components include acid components such as isophthalic acid and adipic acid, and alcohol components such as ethylene glycol, propylene glycol, 1,2- or 1,3-butanediol, and 1,6-hexanediol.

The L-PBT used in the present invention is generally, for example, dimenal terephthalate with an excess of 1 mole of D relative to it,
4-butanediol in the presence of a catalyst, from 130 to 260
It is possible to produce products of any molecular weight by transesterifying at °C and condensing under reduced pressure.

The intrinsic viscosity [η] of the obtained L-PBT can be determined by dissolving L-PBT in a 6:4 mixed solvent of phenol and tetrachloroethane.
Measure at 30°C.

In addition, the hydroxyl value of L-PBT is, for example, Makromole.
-kulare Chem. 17,219-230(
It is determined by reacting the terminal hydroxyl group with succinic anhydride and quantitatively analyzing the resulting carboxyl group, which is described in the literature of 1956).

Examples of the polyfunctional isocyanate used in the present invention include aliphatic diisocyanates such as tetramenal diisocyanate and hexamethylene diisocyanate; tolylene-2,4-diisocyanate and tolylene-2,6-diisocyanate;
Aromatic diisocyanates such as diisocyanate, diphenylmethane-4,4'-diisocyanate, m- and p-phenylene diisocyanate, and naphthalene-1,5-diisocyanate; alicyclic diisocyanates such as dicyclohexylmethane diisocyanate.

Furthermore, 1 such as crude diphenylmethane diisocyanate
Compounds with two or more incyanate groups in the molecule, tolylene diisocyanate dimer, diphenylmethane-4,4
Dimers of '-diisocyanate, incyanurate compounds, etc. can also be used.

The above-mentioned L-PB which is a constituent component of the polyurethane of the present invention
The ratio of T and polyfunctional incyanate is preferably 1:1 for each functional group.

Usually, the number of isocyanate groups per active hydrogen of L-PBT is 0.
．． A ratio of 8 to 1.5 is also acceptable.

During the urethanization reaction, a chain extender such as 1,4-butanediol may be included if necessary, but if the amount of chain extender is large, the amount of incyanate used will also be large, and the final resin composition will be The amount used should be no more than 10% by weight of PBT since it can significantly change the properties of PBT.

Suitable chain extenders include 1,4-butanediol, bishydroxyethyl terephthalate, and the like.

In the composition of the invention, PBT-based polyurethane is
It is also possible to substitute amounts of less than 0% with other polymers.

Examples of such other polymers include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, ethylene-propylene copolymer, polynarene, AS resin, ABS resin, nylon, polyacetal, polycarbonate, polyethylene. Examples include terephthalate, polysulfone, polyphenylene oxide, polyvinyl chloride, chlorinated polyethylene, thermoplastic polyurethanes other than those of the present invention, and polyphenylene sulfide.

The carbon fibers treated with the epoxy resin used in the present invention may be either acrylic or cellulose-based high-rigidity types, or petroleum pitch-based low-rigidity types.

Chopped strand-like fibers having a diameter of 5 to 20 μm and a length of 0.05 to 13 mm, preferably 0.1 to 6 mm are easy to use.

Any known epoxy resin for treating carbon fibers may be used, such as bisphenol A epoxy resin, bisphenol F epoxy resin, resorcinol epoxy resin, novolak epoxy resin, vinylcyclohexene diepoxide, dicyclo Examples include pentadiene diepoxide, various epoxy resins substituted with bromine or chlorine, and bisphenol A type epoxy resin is particularly preferred.

It is also a good practice to directly feed roving-shaped carbon fibers treated with such epoxy resin into an extruder in which the resin has been dissolved.

It should be noted that carbon fibers treated with epoxy resin are less likely to be defibrated, making them easier to handle, and at the same time, their adhesion to the resin is improved, resulting in higher strength.

The amount of carbon fiber treated with epoxy resin is 5% in the composition.
~50% by weight.

If it is less than 5% by weight, the desired properties will not be exhibited and the
If the amount exceeds % by weight, it becomes difficult to disperse the carbon fibers uniformly, the moldability of the composition deteriorates, and the surface condition of the molded product becomes poor.

The production of the composition of the invention involves, for example, chopping strands with a length of 6 mm that have been pre-converged using an epoxy resin;
After uniformly mixing L-PBT and polyfunctional isocyanate, they are put into a single-screw or twin-screw extruder heated to 210-270°C, kneaded, and discharged with a residence time of about 0.5-10 minutes. - Carbon fibers can be dispersed simultaneously with the polyurethanization reaction of PBT, which is efficient.

Alternatively, L-PBT and polyfunctional incyanate may be melt-reacted in advance at 240°C in a high-viscosity reaction vessel, the resulting polyurethane is made into powder, and this and the carbon fibers as described above are extruded in a single-screw or twin-screw extruder. The composition of the present invention can be produced by kneading the composition.

The composition of the present invention includes a crystal nucleating agent, glass fiber, glass powder,
Inorganic fillers, plasticizers, mold release agents, lubricants, heat stabilizers, antioxidants, ultraviolet absorbers, flame retardants, foaming agents, and the like can be added.

In particular, examples of flame retardants include decapromobiphenyl ether, hexabromobenzene, halogenated epoxy resins, halogenated polycarbonate oligomers, ethylene oxide adducts of tetrabromobisphenol A, and halogens obtained from tetrabromobisphenol A and alkyl halides. and a copolymer of enalene oxide adduct of tetrabromobisphenol A and 1,4-butanediol-terephthalic acid.

In addition to these flame retardants, flame retardant aids such as antimony trioxide,
It is more effective to use zinc borate, zirconium oxide, tin dioxide, sodium pyroantimonate, etc. in combination.

EXAMPLES The present invention will be explained in more detail by giving Examples, Reference Examples, and Comparative Examples below.

Reference Example 1 (Synthesis of L-PBT) 194 parts of dimenal terephthalate and 135 parts of 1,4-butanediol were placed in a reaction vessel and heated to 150°C to form a homogeneous solution.

When 0.04 part of tetraisopropyl titanate (catalyst) was added to this solution while stirring under a nitrogen stream, transesterification started and by-product methanol was distilled out.

The temperature in the system was gradually raised, and when the distillation of methanol almost stopped at around 220°C, the system was gradually evacuated to proceed with condensation.

The reaction was carried out at 250° C. and 10 mmHg for 2 hours, and the resulting resin was taken out.

The obtained L-PBT exhibited an intrinsic viscosity [η) of 0.38, a hydroxyl value of 17.5, and an acid value of 0.45.

This is called PBT-1.

Reference Example 2 (Synthesis of L-PBT) It was carried out in the same manner as Reference Example 1, but by extending the condensation time, PBT with an intrinsic viscosity [η] of 0.45, a hydroxyl value of 10.5, and an acid value of 0.72 was produced. Synthesized.

This will be referred to as PBT-2.

Reference Example 3 (Synthesis of PBT) The same procedure as Reference Example 1 was carried out, but the degree of vacuum during condensation was changed to 0.5 m.
mHg, and PBT with an intrinsic viscosity [η] of 1.0 was synthesized.

This is designated as PUT-3. Reference Example 4 (Synthesis of polyurethane) 100 parts of PBT-1 synthesized in Reference Example 1 was placed in a reaction vessel for high viscosity resin, and after melting at 240°C under a nitrogen stream,
While stirring, 5.6 parts of diphenylmethane-4,4'-diisocyanate was added and reacted.

After 5 minutes, the resin was taken out from the reaction vessel. The intrinsic viscosity [η] of the obtained resin was 1.0.

This is referred to as polyurethane-1.

Example 1 66.2 parts of PBT-1 synthesized in Reference Example 1 and carbon fiber [
Manufactured by Toho Rayon; Epoxy resin (Epon 828 and 100)
50/50 ratio mixture of 1; manufactured by Ciel) binder 1.5
Acrylic high rigidity coated with 6m long
m carbon fiber; trade name Besphite RHTA-C6-E
) was added to a Henschel mixer (manufactured by Mitsui Miike), and the stirring blades of the Henschel mixer were rotated at 1640 rpm.
The carbon fibers were stirred at high speed for 30 minutes to cut the carbon fibers into short pieces and uniformly disperse them.

Next, 3.8 parts of diphenylmethane-4,4'-diisocyanate was added and similarly stirred for 1 minute.

The premix thus obtained was heated to a cylinder temperature of 250°C.
It was fed into a 65 mm vented extruder set at .degree.

Extrusion was carried out at a screw rotation speed of 80 revolutions/min.

In this case, the residence time of the resin composition in the cylinder was 90
It was seconds.

The resin composition was extruded in the form of a string, cooled, and cut into pellets.

A test piece according to ASTM was prepared from this pellet using a 3-ounce injection molding machine under conditions of a cylinder temperature of 240° C., an injection pressure of 600 kg/cm 2 , and a mold temperature of 70° C.

[η] of the obtained polymer was 0.9, and the resin composition had a tensile strength (hereinafter abbreviated as TS) of 1400 kg/cm2 and a tensile modulus (hereinafter abbreviated as TM) of 1.8 x 105 Kg/cm3.
, bending strength (hereinafter abbreviated as FS) 2300Kg/cm3,
Flexural modulus (hereinafter abbreviated as FM) 1.5×105Kg/c
m2, notched Izod impact strength (hereinafter abbreviated as N-II) of 8 kg·cm/cm, and non-notched Izod impact strength (hereinafter abbreviated as II) of 65 kg·cm/cm.

Comparative Example 1 In Example 1, PBT-3 was used instead of PBT-1.
0 parts and without diphenylmethane-4,4'-diisocyanate.

The composition is TS1000Kg/m, TM1.0×105
Kg/cm2, FS1600kg/cm2, FM9×1
04kg/cm2, N-II7kg/cm/cm, II
It showed 50 kg·cm/cm.

Comparative Example 2 Chopped glass fiber treated with 370 parts of PBT and an aminosilane coupling agent (trade name: Glasslon C)
S-03-MA411; length 3 mm, manufactured by Asahi Fiberglass) 30.5 parts were mixed in advance for 1 minute in a vertical tumbler, and then kneaded using an extruder in the same manner as in Example 1.

The obtained composition had a TS of 1000 kg/cm2 and a TM9
×104kg/cm2, FS1500kg/cm2, F
M8×104kg/cm2, N-■■7kg・cm/c
m, II was 50 kg·cm/cm.

Comparative Example 3 In Example 1, Besphite HTA-C6-E was heated in advance at a high temperature to eliminate the epoxy binder.

TS of the composition is 1250 kg/cm2, TM1.7×1
05kg/cm2, FS2100kg/cm2, FM1
．． 4×105Kg/cm2, N-II7kg・cm/c
m, II was 62 kg·cm/cm.

Example 2 Three epoxy resins (trade name Epon 1007; manufactured by Ciel) were
% coated 6mm long acrylic high rigidity chopped strand carbon fiber 31 parts and polyurethane-17
Mix 0 parts for 1 minute using a vertical tumbler to make it homogeneous.

This was extruded and kneaded in the same manner as in Example 1.

The composition is TS1600kg/cm2, TM2. O×10
5kg/cm2, FS2500kg/cm2, FM1.
7×105kg/7, N-II10Kg・cm/cm,
II was 75 kg·cm/cm.

Comparative Example 4 In Example 2, carbon fibers treated with epoxy resin were heated in advance at a high temperature to eliminate the epoxy binder.

TS of the composition is 1200kg/cm2, FS1.4×1
05kg/m, FS2050kg/cm2, FM1.5
×105kg/cm2, N-II7kg・cm/cm,
■■50 kg·cm/cm.

Examples 3 to 5 PBT-2, diphenylmethane-4,4'-diisocyanate (MDI) and Besphite HTA-C6-E were blended according to Example 1 in the formulations shown in Table 1 below, respectively.
Extrusion was performed.

The results are also shown in Table-1.

Claims (1)

[Claims] 1. A thermoplastic resin composition comprising a reaction product of polybutylene terephthalate having an intrinsic viscosity of 0.2 to 0.6 and having hydroxyl groups at both ends and a polyfunctional incyanate, and carbon fibers treated with an epoxy resin.