JPS61174262A - Resin composition - Google Patents

Abstract

PURPOSE:To provide a resin compsn. which has excellent moldability, gives moldings which does not cause warpage and is suitable for use as a molding material for the production of high-accuracy precision parts, containing a crystalline thermoplastic resin, a carbon fiber and mica flake. CONSTITUTION:A crystalline thermoplastic resin (A) (e.g. polyamide resin), a pitch or acrylic carbon fiber (B) having a ratio of number-average fiber length to number-average fiber diameter of 7-60 and a mica flak (C) (e.g. high-purity natural mica having a mica content of 80% or above) having a ratio of number- average length of major axis to that of minor axis of 5 or below and a ratio of number-average length of minor axis to number-average diameter of minor axis of 20 or above, are mixed in such a proportion as to satisfy the relationship of formulas I, II (% in weight). The mixture is melt-kneaded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resin composition containing a crystalline thermoplastic resin, carbon fiber (CF), and mica flakes (MF). Since warpage does not occur in fiber-reinforced thermoplastic resin molded articles made from this composition, the resin composition of the present invention is particularly useful as a molding material for precision parts.

[Prior art]

Carbon fiber reinforced thermoplastic resin (CFRTP) has excellent mechanical and electrical properties, and is even better! Due to its moldability, its use in industrial materials has been increasing in recent years.
There is something remarkable.

Among them, polyamide resin, polyacetal resin, polyethylene terephthalate resin, polybutylene terephthalate 1
- CF in crystalline thermoplastic resins such as resins, polyphenylene sulfide resins, and polyetheretherketone resins
When added, the thermal deformation leakage, which is the target of the upper limit of concentration used, increases to near the melting point of the resin. As a result, it has become possible to use resins at temperatures that were previously considered impossible to use alone. On the other hand, crystalline thermoplastic resins have a large molding shrinkage rate and are prone to anisotropy, resulting in warpage in thin-walled molded products. When CF is added to a crystalline thermoplastic resin, the anisotropy of the molding shrinkage rate becomes greater than when the resin is used alone, and the degree of warpage becomes even greater. Therefore, it has become difficult to use CF-reinforced crystalline thermoplastic resins for molded products that require high precision. For precision parts, non-grade thermoplastic resins such as polycarbonate resin, polysulfone resin, and modified polyphenylene oxide resin with low mold shrinkage and low anisotropy are used as base materials. Even when added, the heat distortion temperature hardly increases, resulting in a low upper limit temperature for use and a high melt viscosity, which results in poor moldability.

Mr. Mizumoto conducted extensive studies to improve the warpage of the CF-reinforced crystalline thermoplastic resin described above, and as a result, he arrived at the present invention (S).

[Structure of the invention]

The present invention consists of crystalline thermoplastic resin (△) and carbon fiber (B).
and mica flakes (C). With the resin composition having such a structure, a molded product without warpage can be obtained.

The particularly preferred ratio of each component (A>, (B), and (C) of the present invention is B+C 15%≦(X 100≦50% (wt%)) A −1−
B + C, and 30%≦(-)x100≦60% (wt%) B+C.

Number average fiber length (ρ) and number average fiber length f of carbon fiber (A)
The ratio R/d, f with M(df) is preferably 7 to 60. Mica flakes have long sleeves with an average length of 1S of 5 or less,
and the number average length of the short axis (ds) and the number average value of the thickness (1)
It is preferable that the ratio is 20 or more. When the resin composition of the present invention is used, the excellent properties of the CF-reinforced crystalline thermoplastic resin are not impaired, and precision parts with less warpage can be molded.

Examples of the crystalline thermoplastic resin in the present invention include polyamide resin, polyacetal resin, polybutylene prephthalate resin, polybutylene prephthalate resin, polyphenylene sulfide resin, polyether needle ketone resin, polyolefin resin, and the like.

The CF in the present invention may be, for example, pitch-based or Acuzino 1-based CF, and may be either carbonaceous or graphitic. The dimension of CF in the base resin is preferably such that Ltd/df, which is the number average fiber length (l) and the number average fiber diameter (df), is in the range of 7 to 60.

That is, the mechanical strength and elasticity of the molded product increase in proportion to the Q/d of the CF, but as this value increases, the moldability deteriorates, and as this value decreases, the reinforcing effect of the CF decreases. More preferably, R/df is in the range of 20 to 50. The number average fiber length of CF is
In order to prevent the dimension of F from changing, it can be determined by, for example, chemically decomposing the resin, separating the resin and CF, and then measuring the length of each fiber.

The mica flakes used in the present invention may be either natural or artificial as long as they have cleavability. Natural mica is an aluminum silicate mineral, and contains muscovite, phlogopite, biotite, soda mica, rhodotite, iron mica, etc. as its main components, as well as pyroxene, feldspar, apatite, calcite, etc.1 ．． High purity mica refined to a mica content of 80 or higher is particularly preferred. Alternatively, artificial mica in which the OH group of mica is substituted with F (fluorine) may be used. Regarding the dimensions of the mica flakes in the base material resin, it is preferable that the ratio d, Q/ds, of the number average length (di) of the major axis to the number average length (ds) of the minor axis is 5 or less.

When the value exceeds 5, the effect of weighting against warping becomes smaller. Also, the ratio dS of the number average length of the minor axis (ds) and the number average value of the thickness (1)
/l is preferably 20 or more, particularly 30 or more.

If this ratio ds/, t is less than 20, the effect on damage will be small. The dimensions of the mica flakes can be determined by separating the mica flakes from the resin and measuring the length of each mica flake one by one in the same manner as CF. Even if CF and mica flakes coexist, they can be easily distinguished because they have different forms.

In addition, crystalline thermoplastic resin (A) and CF (B) as base materials
and mica flakes (C): B to C 15%≦()x100≦50% (weight%) A +, B
+ C and 30%≦←−−) X 100≧60% (weight %)B+C. (B+C)'/(A+B+C
) When x100 is less than 15% by weight, the reinforcing effect of CF and mica flakes on the molded product is small, and when it exceeds 50% by weight, moldability deteriorates. Also C/ (B
When +'C)

The resin composition of the present invention may be in any form, including pellets obtained as follows.

CF chopped fibers with a length of 1 to 6 mm, mica flakes with a short axis of 20 to 1000 μ and a thickness of 1 to 20 μ, and crystalline thermoplastic resin pellets or powder are premixed in a tumbler, etc., and then extruded. Melt and knead, diameter 2
The extruded strands to ~4 mm are cut into lengths of 2 to 6 mm to obtain pellets.

〔Effect of the invention〕

As described above, according to the present invention, by using a resin composition containing a crystalline thermoplastic resin, carbon fiber, and mica flakes in a specific ratio, the warpage of the molded product is significantly reduced. In addition to improving processability, it has become possible to mold high-precision, precision parts.

(Example) Example 1 70% by weight of nylon 66 with a viscosity average molecular weight of 2 x 10'', 15% by weight of acrylic CF with a diameter of 7μ and a thickness of 6mm as shown in Table 1, and the following composition formula: 2 (M(1 *
,tFe+,zAQo,+)(Sis,gA1!z,s
)020 (OH)2 Phlogopite (suzolite mica manufactured by Kuraray Co., Ltd.) 1, which is somewhat similar to biotite and is indicated by F2.
After weighing to 5% by weight, it was mixed in a tumbler and extruded under the extrusion conditions shown in Table 1 using a 40 mm diameter open vent type single screw extruder (Scricoe length/screw diameter -28).
Melt and knead to extrude strands of 2 to 4 mm,
After cooling in a water tank, it was cut into 6 mm pieces to obtain resin composition pellets! In order to measure the length, the resin of this pellet was decomposed with hot concentrated sulfuric acid and hydrogen peroxide solution, and CF and mica flakes were separated. 1 for each 500 lengths of CF and mica flakes
The length was measured under 00x magnification and the number average value was determined. The thickness of the mica flakes was determined by measuring the length from an electron micrograph magnified 1000 to 2000 times.

The obtained pellets were dried under reduced pressure and heated to a water absorption rate of 0.1%.
After reducing the temperature to below, use a 5 oz in-line screw injection molding machine with a cylinder temperature of 300℃, a mold temperature of 11ioo℃,
Injection pressure 1200kof/cni', holding pressure 600k
The specimens were molded at gf/cm'.

The test pieces are JISI dumbbell test pieces for tensile tests.
12.7X 4.0X63.5 for Izotsu impact test
mm square bar, 100x 10100 for warpage rate test
X2 (1.5n+m thick film gate at i end)
A flat plate was provided. Tensile test is JIS K-711
3. Izot impact test is J Is K-7110,
The warpage rate was based on JIS K-6911. Immediately after molding, the test piece was left in a vacuum dryer at 23° C. and 10 mmH (I) for 48 hours, and then tested.

The results are shown in Table 1.

For comparison, 85% by weight of nylon 6G shown in Example 1
As shown in Table 1, 15% by weight of CF was added to MF.
A system without the addition of CF or MF and a single system of the nylon without the addition of CF or MF were melt-kneaded in an extruder using the extrusion strip f1 shown in Table 1 and pelletized to obtain each pellet.

Table 1 shows the properties of the resin composition and the molded products obtained by molding test pieces under the same conditions as in Example 1 and testing under the same conditions.

As seen in Table 1, it can be seen that the resin composition of the present invention has a reduced warpage rate compared to the system to which CF is added but no MF, and the nylon 66-only system.

Table 1 Example 2 Nylon 6G and CF15% by weight used in Example 1 and II
Mica flakes with an average flake size of 280 μm and an average thickness of 4.0 μm were premixed in a tumbler in the proportions shown in Table 2, and then heated using the extruder used in Example 1 at a cylinder temperature of 30 μm.
0℃, screw rotation speed 900 rpm, extrusion pressure 20k
A resin composition having a diameter of 2 to 4 mm and a length of 6 mm was obtained by pelletizing at gf/cm'.

The properties of these resin compositions were measured in the same manner as in Example 1. The results are shown in Table 2.

In addition, a test piece was molded in the same manner as in Example 1, and its properties were measured.

The results are shown in Table 2. The results for the 15% by weight CF system are also listed in Table 2.

As shown in Table 2, C/ (, B + C) x 100
(7) It can be seen that the effect of mica flakes against warpage and the strength of the molded product are particularly excellent in the weight range of 30 to 60% by weight.

Table 2

Claims (4)

[Claims] (1) A resin composition containing a crystalline thermoplastic resin (A), carbon fiber (B), and mica flakes (C). (2) The ratio of crystalline thermoplastic resin (A) to carbon fiber (B) to mica flakes (C) is 15%≦[(B+C)/(A+B+C)]×100≦5
0% (weight%), and 30%≦[C/(B+C)]×100≦60% (weight%
) The resin composition according to claim (1). (3) Claim (1) wherein the ratio of the number average fiber length (@l@) to the number average fiber diameter (@d@f) of the carbon fibers @l@/@d@f is 7 to 60. Resin composition. (4) Number average length of long axis of mica flakes (@d@l)
and the number average length of the minor axis (@d@s) @d@l/@d@
Claims in which s is 5 or less and the ratio of the number average length (@d@s) to the number average thickness (@t@) of the short axis @d@s/@t@ is 20 or more ( 1) Resin composition.