JPH0637066B2 - Polyamide resin precision injection molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polyamide resin composition containing polyamide-12 (12-nylon) as a main component and a polyamide-12 resin as a main component, and polyetheramide as a main component. The present invention relates to a polyamide resin precision injection molded article obtained by precision injection molding.

The injection-molded article of the present invention is an injection-molded article obtained by using a polyamide resin composition of a polyamide-12 resin containing a specific polyamide-12 as a main component and a polyetheramide (polyamide elastomer). The traces on the gate of the injection-molded product, especially the traces on the gate of the injection-molded product obtained by injection molding from a mold that uses a gate with a small gate diameter, such as a pinpoint gate, are extremely small. Since only a small amount remains and the appearance of the gate part is very good, there is no need for post-processing to remove the traces of the gate part with a cutter knife etc. Furthermore, injection molding obtained during precision injection molding The dimensional accuracy of the body is stable.

[Description of Prior Art] Conventionally, polyamide-12 has little dimensional change due to moisture absorption, has relatively high heat resistance, is extremely good in abrasion resistance, abrasion resistance, and the like, and further contains a plasticizing filler. As a result, since it is possible to easily impart flexibility, it is used as a polymer material for precision injection molding such as gears and bushes.

In the case of precision injection-molding a part made of the above-mentioned injection-molded body, the mold used is mostly a pinpoint gate because of the shape and function of the molded body. For example, see FIG. 1 (a). As shown in FIG.
Injection-molded article 1 obtained by precision injection molding from a die adopting the pinpoint gate, using a resin of the series
In the above, the cut 2 at the gate portion remains considerably large, and it is necessary to perform post-processing to cut and remove this cut with a cutter knife or the like.

In addition, polyether ester amide, polyether amide, etc. have been proposed as polymer materials that can reduce the number of gate marks on the injection-molded body in the precision injection molding described above. Although the traces became very small, the friction and wear resistance deteriorated, and in the case of injection molded products such as gears, the protrusions (tips) of the injection molded products were worn or deformed during use. There is a "sink problem" such as the fact that the use of these polymer materials in precision injection molding was limited to the molding of special parts.

Further, the polyether amide has other problems such as surface discoloration or dents (sink marks) in the molded injection-molded article, and poor releasability from the mold.

[Problems to be solved]

The object of the present invention is to provide a precision injection molding machine in which the mold used is an injection molding machine provided with a mold having a gate with a small gate diameter such as a pinpoint gate. As shown in (b), the gate marks 4 of the gate portion of the injection molded body 3 obtained by precision injection molding.
However, only traces remain, post-processing to remove the traces is not substantially required, and discoloration or dents (sinks) do not occur, and dimensional stability is further improved. Therefore, an excellent injection-molded article having high abrasion resistance or abrasion resistance has not been obtained in the past, and it is an object of the present invention to provide a suitable precision injection-molded article as described above.

[Main requirements of the present invention]

As a result of intensive studies to solve the above-mentioned problems in the known art, the present inventors have found that a polyamide-12 resin containing polyamide-12 as a main component and a polyether amide are blended in a specific ratio. With a precision injection molding machine equipped with a mold having a gate with a small gate diameter such as a pinpoint gate, using a resin composition, when precision injection molding is performed, the gate marks on the injection molded body will be traces. It is extremely small, and there are no dents or discolored parts on the injection-molded product.
It was found that a precision injection-molded article excellent in abrasion resistance and abrasion resistance can be obtained, and the present invention was completed.

That is, the present invention has (a) a relative viscosity ηr (JIS K-6810) of 1.5.
To 3.2, preferably about 1.8 to 2.8, and 100 parts by weight of a polyamide-12 resin which mainly contains polyamide-12, and (b) a relative viscosity ηr (measurement temperature; 25 ° C., Concentration; 0.5
g / 100 ml solvent, measuring solvent; meta-cresol) is from 1.1 to 2.0, preferably from 1.2 to 1.8, 25 to 400 parts by weight, preferably 3
Precision injection molding of polyamide resin obtained by precision injection molding with a precision injection molding machine equipped with a mold having a gate diameter of 2.0 mm or less from a polyamide resin composition containing 0 to 360 parts by weight as a main component. Regarding a molded body.

[Detailed description of each requirement of the present invention]

Polyamide-12 used in this invention is ε-
A polyamide-12 having the above-mentioned relative viscosity obtained by self-polycondensation from monomers such as aminododecanoic acid and laurinlactam may be used, and as the above-mentioned polyamide-12, about 20 mol% or less of the monomer component,
Particularly preferred is a polyamide-12 copolymer in which 10 mol% or less is replaced with a repeating unit based on another monomer component (caprolactam, a salt of hexamethylenediamine and adipic acid, undecane lactam, etc.).

As the polyamide-12 resin used in the present invention,
The polyamide-12 (including a polyamide-12 copolymer) as a main component (preferably 80% by weight or more,
Polyamide-12 resin containing 90% by weight or more) is particularly preferable.

As the polyamide-12 resin, polyamide-6 other than polyamide-12, nylon-6, nylon-
20% by weight or less, particularly preferably 10% by weight or less, of 6,6, nylon-11 and the like may be contained.

The polyether amide used in this invention includes (A) a polyamide moldable monomer and (B) a general formula H ₂ N—R ¹ —O— (R ² —O) n—R ² —NH ₂ . in the diamine compound represented (wherein, ^{R 1} and ^{R 2} are each an alkylene group having 3 or more carbon atoms, n represents 2
(About 60) and (C) a compound having a carboxyl group at both ends, which is obtained by copolycondensation.

Examples of the polyamide moldable monomer (A) include ε-
Examples thereof include a lactam compound, an ε-aminocarboxylic acid compound, and a salt of a carboxylic acid compound and a diamine compound. Examples of the ε-lactam compound include caprolactam, enantolactam, decalactam, undecanelactam, dodecanelactam and the like. Examples of the ε-aminocarboxylic acid compound include 6-aminocaproic acid, 10-aminodecanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid and the like. The salt of a carboxylic acid compound and a diamine compound, ethylenediamine, trimethylenediamine, tetraethylenediamine, hexamethylenediamine, undecamethylenedimine, dodecamethylenediamine, 2,2,4- or 2,4,4-trimethylhexamethylene Diamine, 1,3-or
1,4-bis (aminomethyl) cyclohexane, bis (4,4 '
-Aminocyclohexyl) methane, a diamine compound such as m- or p-xylylenediamine, and oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, 1 Mention may be made of various salts with dicarboxylic acid compounds such as 1,4-cyclohexanedicarboxylic acid, terephthalic acid and isophthalic acid.

The terminal aminopolyoxyalkylene (B) represented by the above general formula has a linear or branched oxyalkylene repeating unit having 3 or more carbon atoms in the molecular chain, and both ends of the molecular chain Is a polyether diamine compound having an amino group, for example, propylene oxide,
It can be synthesized by introducing an amino group into the terminal of a polymer obtained by homopolymerization or copolymerization of tetrahydrofuran.

In the above general formula, n is preferably 4-40.

The terminal aminopolyoxyalkylene (B) has at least 50 oxyethylene repeating units in its main chain.
It also contains a polymer having a mol%, such as polyoxypropyleneamine, bis (3
-Aminopropyl) polytetrahydrofuran and the like.

The compound (C) having a carboxyl group at both ends used in the present invention is an aliphatic dicarboxylic acid having 10 to 50 carbon atoms, and is obtained by coupling oleic acid, linoleic acid, linolenic acid, etc. Preferred dimerized aliphatic dicarboxylic acid (dimer acid), or a polybutadiene hydrogenated product having a carboxyl group at both ends produced by hydrogenating a polybutadiene having a carboxyl group at both ends may be preferably mentioned. it can.

As the above-mentioned dimer acid, those having a relatively small amount of unsaturated bonds are preferable, and the hydrogenation rate is particularly preferably about 90% or more.

As the hydrogenated polybutadiene, 1,2-bond,
It may contain any micro bond such as 1,4-trans bond and 1,4-cis bond. Hydrogenation of polybutadiene having a carboxyl group at both ends, nickel as a catalyst,
A solid or soluble complex of cobalt, platinum, palladium, rhodium or the like is used alone or in a mixed system, and the reaction temperature is room temperature to 200 ° C., particularly preferably room temperature to 150 ° C. In the presence of hydrogen,
It is carried out by a known general method.

The above polybutadiene preferably has a hydrogenation rate of 80% or more, particularly 90% or more, and a polybutadiene hydrogenation product having a carboxyl group at both ends of 60% or more, particularly preferably 75% or more is used. The molecular weight is preferably about 500 to 50,000, and particularly preferably about 800 to 10,000.

The polyamide resin composition used for precision injection molding in the present invention comprises 100 parts by weight of the polyamide-12 resin containing the above-mentioned polyamide-12 as a main component and 25 to 400 parts by weight of the above-mentioned polyetheramide as the main components. (The content of the total amount of the above-mentioned polyamide-12 resin and polyether amide with respect to the total amount of the polyamide resin composition is 60% by weight or more, and particularly 70% by weight or more).

In this invention, in the above polyamide resin composition,
If the blending ratio of the polyether amide is too large, the injection molded body obtained by precision injection molding using such a polyamide resin composition may be deformed when the mold is released from the mold, or the protrusions may be formed. It is not suitable when an injection-molded product such as a gear having a tooth is molded, because the protrusion (tooth) of the molded product may be deformed or worn. On the other hand, the proportion of polyetheramide compounded When the amount is too small, the injection molding obtained by precision injection molding using such a polyamide resin composition has large gate marks in the thin gate portion, and post-processing for removing the gate marks. Is required, so it is not appropriate.

The polyamide resin composition used in the present invention contains a plasticizing filler in an amount of 1 to 40 for the purpose of imparting flexibility.
%, Particularly preferably 2 to 30% by weight,
It is preferable for further improving the physical properties of the injection molded product.

The plasticizing filler may be of any type, as long as it is generally used for polyamide resins, in particular, benzenesulfonic acid butylamide,
2-ethyl-hexyl-p-hydroxybenzoate,
Alternatively, a mixture thereof or the like is generally used.

Further, in the present invention, the polyamide resin composition,
Stabilizers against heat and light such as heat deterioration inhibitors, ultraviolet absorbers, and antioxidants, nucleating agents (for example, inorganic fillers; talc,
A small amount of known modifiers such as kaolin and wollastonite) and release agents (for example, metal salts of higher fatty acids and low molecular weight polyethylene wax) may be contained.

As the compounding method of the polyamide resin composition, a compounding method generally used for compounding a polyamide with another thermoplastic resin can be adopted, and for example, polyamide-12 in a sufficiently dried pellet form can be used. A method of blending a resin and a polyether amide in a desired blending ratio with a Brabender or the like, and a method of melt-mixing a polyamide-12 resin and a polyether amide with a melt extruder and pelletizing and blending. And the like can be preferably mentioned.

The precision injection molding in the present invention uses a high-pressure type injection molding machine, plasticizes and melts the above polyamide resin composition in a cylinder, and injection-fills the molten resin into a mold cavity under predetermined conditions. Any ordinary injection molding method may be used.

The precision injection-molded article of the present invention has, for example, a gate diameter of 2.
It is molded by injection molding using various known precision injection molding machines in which a mold having a large number of pinpoint gates of 0 mm or less, particularly preferably 1.5 mm or less is used.

The injection molding temperature in the precision injection molding is 180 to
It is preferably about 250 ° C.

In the mold of the injection molding machine, the gate length,
The gate position, cavity shape, etc. are not particularly limited.

Further, in molding the precision injection-molded product according to the present invention, the injection pressure, the injection speed, the injection pressure, the injection speed, the burr, the sink mark, and the residual stress near the gate of the molded product are minimized.
Conditions such as mold cooling time, storage, cavity shape,
It is necessary to set it according to the gate position and the number of gates.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to examples. In addition, in the following Examples and Comparative Examples, the length of the gate portion of the injection-molded article after the gate was cut was measured using the module 0.
5, number of teeth 65, pitch circle diameter 32.5 mm, outer diameter 33.5
mm, tooth width 3.0 mm, with a cavity for molding a gear, using a gear mold with a pin point gate with a gate diameter of 1.0 mm The length of the scar was measured with a scaled loupe.

The appearance of the injection-molded article was also evaluated using the gear injection-molded article.

The measurement of the raw meshing error is performed by using the injection molded body of the above gear,
The measurement was performed using a meshing tester (GTR-4 type, manufactured by Osaka Precision Machinery Co., Ltd.).

Furthermore, regarding the degree of deformation and wear of the teeth of the gear injection-molded body (degree of settling), the meshing between the injection-molded body of the present invention and the same polyacetal gear-molded injection-molded body as the injection-molded body of the present invention The rotation speed is 1500 rpm, 4
After the 00-hour meshing test, the degree of settling of the addendum of the injection-molded article of the present invention was visually evaluated.

Reference Example 1 [Production of Polyetheramide (E1)] 50 parts by weight of ε-aminododecanoic acid and 22.85 parts by weight of dimer acid (Empol 1010, manufactured by Emery Co.) were charged in a polymerization vessel and then 240 After polymerization at 4 ° C. for 4 hours, polyoxypropylene amine (Jefferson Chemical Co., Jefferson D-400) 2
3.3 parts by weight and 3.85 parts by weight of meta-xylenediamine were further charged into a polymerization vessel, and the mixture was placed under a nitrogen atmosphere for 24
Polycondensation was performed at 0 ° C. for 6 hours to obtain a colorless transparent polymer. This polymer was extruded with a melt extruder, cooled in water, pelletized with a pelletizer, and dried under reduced pressure. Relative viscosity of the obtained polyetheramide (E1) (measurement temperature; 25 ° C., measurement concentration; 0.5 g / 100 ml)
The solvent and the measurement solvent; metacresol) were 1.54.

Reference Example 2 [Production of Polyetheramide (E2)] 70 parts by weight of ε-aminododecanoic acid and 13.7 parts by weight of dimer acid (Empol 1010, manufactured by Emery Co.) were charged in a polymerization vessel and polymerized under a nitrogen atmosphere. At a temperature of 240 ° C,
After polymerization for 4 hours, polyoxypropylene amine (Jefferson Chemical Co., Jeffamine D-40
0) 14.0 parts by weight, and meta-xylene diamine 2.
Further, 3 parts by weight was charged into a polymerization vessel, and under a nitrogen atmosphere,
A colorless transparent polymer was obtained by polycondensation at 240 ° C. for 6 hours. This polymer was extruded with a melt extruder, cooled in water, pelletized with a pelletizer, and dried under reduced pressure. Relative viscosity of the obtained polyetheramide (E1) (measurement temperature; 25 ° C., measurement concentration; 0.5 g / 100 ml)
The solvent and the measurement solvent; metacresol) were 1.80.

Examples 1 to 7 and Comparative Examples 1 to 8 As a polyamide-12 resin, the relative viscosity η shown in Table 1 is shown.
The composition ratio of polyamide-12 and plasticizer shown in Table 1 (polyamide-12) is used.
/ Plasticizer; weight ratio) was prepared.

The polyamide-12 resin (PA-1, PA-2 or PA-3) of the above Table 1 in the use amount shown in Table 2 and the polyetheramide of Reference Example 1 or 2 in the use amount shown in Table 2 ( E
1 or E2) and a polyamide resin composition prepared by blending with a Henschel mixer. Module 0.5, number of teeth 65, pitch circle diameter 32.
Using a precision injection molding machine equipped with a gear mold having a gear cavity of 5 mm, an outer diameter of 33.5 mm, and a tooth width of 3.0 mm, and a pin point gate of 1.0 mm in diameter, The injection-molded body of 1 was injection-molded.

Then, the length of the gate cut of the gate portion of the obtained injection molded body, the presence or absence of discoloration or dent (sink), the presence or absence of deformation, the total engagement error, and the wear of the tooth tip after the engagement test (slip)
The presence or absence of was measured.

The results are shown in Table 2.

[Operation and Effect of the Present Invention] The polyamide resin precision injection-molded product of the present invention is pinpointed by using a polyamide resin composition in which a specific polyamide-12 resin and a polyetheramide are mixed in a specific mixing ratio. A precision injection molding machine equipped with a mold that has an extremely thin gate part such as a gate shows the gate trace of the gate part obtained by injection molding as shown in Fig. 1 (b).
It is an injection molded body that leaves only traces as shown in
As a result, this injection-molded body does not require post-processing to remove gate marks.

Further, the injection-molded article of the present invention has no discoloration or dent (sink), has excellent dimensional stability, hardly undergoes deformation when released from the mold, and has an injection-molded article such as a gear. In the case where the gear is injection-molded, when the gear is used, there is substantially no deformation / wear (deterioration) of the protrusion (tooth) of the gear.

[Brief description of drawings]

FIG. 1 (a) is an enlarged cross-sectional view showing a cut portion of a gate portion in an injection-molded article according to the prior art.
(b) is an enlarged sectional view showing a cut portion of the gate portion of the injection-molded article according to the present invention. DESCRIPTION OF SYMBOLS 1; Conventional injection molded product, 2; Trace of gate portion of conventional injection molded product, 3; Injection molded product of this invention, 4;
Traces of the gate portion of the injection-molded article of the present invention.

Claims (1)

[Claims] 1. 100 parts by weight of a polyamide-12 resin containing polyamide-12 as a main component and having a relative viscosity ηr (JIS K-6810) of 1.5 to 3.2, and a relative viscosity ηr.
(Measurement temperature: 25 ° C, measurement concentration: 0.5 g / 100 ml
A mold having a gate having a gate diameter of 2.0 mm or less from a polyamide resin composition containing 25 to 400 parts by weight of a polyetheramide having a solvent of 1.1 to 2.0 as a solvent and a solvent of meta-cresol. Precision injection molding of polyamide resin obtained by precision injection molding with a precision injection molding machine equipped with.