JPH0651836B2 - Injection molding method of polyethylene terephthalate resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an injection molding method of a polyethylene terephthalate resin composition having improved moldability and physical properties.

<Prior Art> Polyethylene terephthalate has excellent mechanical properties, chemical properties and electrical properties, and is widely used as fibers and films. However, as is well known, especially when used as an injection molded product for plastic product applications, polyethylene terephthalate has a slow crystallization rate, and therefore, when a molding die of 100 ° C. or less is used, the molded product is It has been pointed out that there are drawbacks such as poor shape stability and dimensional stability and markedly deteriorated appearance of the surface of the molded product. Therefore, in the conventional injection molding of polyethylene terephthalate, it was necessary to use a high temperature mold of 130 ° C. or higher, but at such a high mold temperature, the molding cycle becomes long, which is extremely disadvantageous in terms of productivity.
Against this background, many proposals have been made to accelerate the crystallization of polyethylene terephthalate and improve the above-mentioned drawbacks. Most of the proposals are to add compounds such as a crystal nucleating agent and a crystallization accelerator of polyethylene terephthalate, and as a typical example, inorganic fine particles such as talc (Japanese Patent Publication No. 44-7542), alkali of organic carboxylic acid, etc. A combination of a metal salt compound (Japanese Patent Publication No. 48-4097), a sodium organic carboxylate and a low molecular weight plasticizer compound (JP-A-54-1).
No. 58452) is known.

<Problems to be Solved by the Invention> The present inventors have studied polyethylene terephthalate-based resin compositions that can be injection-molded at a normal mold temperature of less than 100 ° C., and various types such as those shown in the above-mentioned prior examples. It was confirmed that the crystallization accelerator of 1 was effective in improving the moldability, but one of the other drawbacks of polyethylene terephthalate was the hydrolysis resistance and the effect of improving brittleness. It was hard to say that is extremely large. That is, the polyethylene terephthalate-based material, which has a really high practical value, not only has improved injection moldability, but also hydrolysis resistance and impact resistance are problems to be improved at the same time.

<Means and Actions for Solving Problems> Therefore, the inventors of the present invention have obtained a sufficiently crystallized molded product having releasability even when injection molding is performed using polyethylene terephthalate using a mold having a temperature of less than 100 ° C. A study was conducted on a method for producing a molded product that exhibits good hydrolysis resistance and excellent toughness, and it is extremely effective to blend polyethylene terephthalate with a polyamide consisting of hexamethylenediamine, adipic acid and terephthalic acid. The present invention has been achieved by finding that the objective is achieved.

That is, the present invention uses a resin composition comprising (A) polyethylene terephthalate of 60 to 98% by weight and (B) hexamethylenediamine, adipic acid and terephthalic acid of polyamide of 2 to 40% by weight at a mold temperature of 100 ° C. or lower. The present invention provides an injection molding method, which is characterized in that

The (A) polyethylene terephthalate used in the present invention is obtained by a condensation reaction of ethylene glycol and terephthalic acid or its ester-forming derivative. Regarding the degree of polymerization of polyethylene terephthalate used here, a phenol / tetrachloroethane mixed solvent (6/4
The intrinsic viscosity measured at 30 ° C. by weight ratio) is preferably 0.4 or more.

The polyamide (B) composed of hexamethylenediamine, adipic acid and terephthalic acid used in the present invention is obtained by polymerizing these components by a usual method. There is no limitation on the degree of polymerization of the polyamide used here, and the relative viscosity of a 1% concentrated sulfuric acid solution measured at 25 ° C. is 2.0 to 5.0.
Any polyamide within the range can be selected.

The resin mixture of the present invention comprises (A) 60-98% by weight of polyethylene terephthalate, preferably 70-95% by weight and (B) 2-40% by weight of polyamide consisting of hexamethylenediamine, adipic acid and terephthalic acid, preferably 5- It is composed by blending 30% by weight.
If the amount of polyamide is less than 2% by weight, the effect of improving the moldability, hydrolysis resistance, impact resistance, anisotropy of physical properties and the like of polyethylene terephthalate is small, which is not preferable. On the other hand, when the content of polyamide exceeds 40% by weight, the miscibility with polyethylene terephthalate decreases,
It is not suitable because the operation stability when the compound is discharged from an extruder is deteriorated, the oxidation deterioration resistance which is a defect of polyamide is deteriorated, the rigidity is reduced due to water absorption, and the dimensional change is remarkable. Further, for practical use of polyethylene terephthalate material, it is usual to add a reinforcing material such as glass fiber. In this case, the reinforcing material is added to 100 parts by weight of polyethylene terephthalate and polyamide in total.
It is suitable to add and blend 3 to 100 parts by weight. The composition at this time is approximately polyethylene terephthalate: 40 to 7
2.5% by weight, polyamide consisting of hexamethylenediamine, adipic acid and terephthalic acid: 2.5 to 10% by weight, reinforcing material: 25 to 50% by weight.

The method for producing the resin mixture of the present invention is not particularly limited, and a method in which polyethylene terephthalate and a resin group polyamide bicomponent are pre-mixed or not, and the mixture is supplied to a single-screw or multi-screw extruder and melt-kneaded is most common. is there. The mixture thus obtained is subjected to injection molding, and when the mold temperature at that time is set to 100 ° C. or less, a sufficiently crystallized molded product having excellent characteristics can be obtained. An injection molding die that exceeds 100 ° C. is a waste of energy and is not particularly required in the present invention.

The moldability of the resin mixture of the present invention, other components as long as the physical properties are not impaired, such as pigments, dyes, reinforcing materials,
Fillers, heat-resistant agents, antioxidants, weathering agents, lubricants, crystal nucleating agents, release agents, plasticizers, flame retardants, antistatic agents, and other polymers can be added and introduced. In particular, it is important to add reinforcing materials and fillers, and fibrous or powdery reinforcement of glass fiber, asbestos fiber, carbon fiber, graphite fiber, wollastonite, talc, calcium carbonate, mica, clay, potash whiskers, glass beads, etc. A material can be added and compounded. Of these, it is preferable to use a fibrous reinforcing material such as glass fiber or carbon fiber.

The injection-molded article obtained by the present invention is useful as various automobile parts, machine parts, electric / electronic parts, general sundries and the like.

<Examples> The present invention will be described in more detail with reference to Examples.
The properties of the polymers and molded articles described in Examples and Comparative Examples were evaluated by the following methods.

(1) Relative viscosity of polyamide: JIS K6810 (2) Intrinsic viscosity of polyester: Polymer was dissolved in a phenol / tetrachloroethane mixed solvent (6/4 weight ratio) and measured at 30 ° C.

(3) Tensile properties: ASTM D638 (4) Bending properties: ASTM D790 (5) Izod impact strength: ASTM D256 (6) Dimensional stability: Tensile dumbbell test pieces after molding were heat-treated in an oven at 130 ° C for 15 hours. The dimensional change rate was calculated.

(7) Hydrolysis resistance: Tensile test pieces were treated with boiling water, and the time required for the tensile strength to become half the initial value was determined.

(8) Deformation amount of warp: A square plate having a size of 80 mm × 80 mm × 2 mm was injection-molded, placed on a flat base, and one end was pressed against the base, and the distance from the other end was measured.

Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.65 was prepared from ethylene glycol and terephthalic acid by melt polymerization. 70% by weight of substantially equimolar salt of hexamethylenediamine and adipic acid and 30% by weight of substantially equimolar salt of hexamethylenediamine and terephthalic acid were melt-polymerized to prepare nylon 66 / 6T having a relative viscosity of 2.50.

30 parts by weight of chopped strand glass fiber was added to 100 parts by weight of polyethylene terephthalate: 80% by weight and nylon 66 / 6T: 20% by weight, which were then premixed, and then 290 using an extruder with a diameter of 65 mm. It was melt-kneaded and pelletized at ℃. After drying the pellets, a cylinder temperature of 290 was obtained using an injection molding machine.
Test pieces for measuring various physical properties were molded under conditions of ℃ and mold temperature of 95 ℃, and the characteristics of the test pieces obtained here were evaluated. As shown in Table 1, fully crystallized polyethylene terephthalate of high practical value was obtained. It was found to be a system material.

Comparative Example 1 After adding 30 parts by weight of chopped strand glass fibers to 100 parts by weight of polyethylene terephthalate used in Example 1, melt kneading and injection molding were performed by an extruder in the same manner as in Example 1 to obtain a test piece. Obtained. It was found that the dimensional stability of the test piece obtained here was poor and crystallization did not proceed sufficiently during molding.

Dimensional change due to heat treatment: 0.35% Comparative Example 2 A test piece was obtained by repeating the same operation as in Example 1 except that the mixing ratio of polyethylene terephthalate and nylon 66 / 6T was 50/50% by weight. This test piece was markedly colored during the heat treatment and revealed the poor oxidation resistance of nylon.

Examples 2-5 Types of polyethylene terephthalate and polyamide,
The same operation as in Example 1 was performed while changing the compounding amount and the like, and the physical properties of the test piece obtained were measured, and the results shown in Table 1 were obtained.

<Effects of the Invention> In the present invention, a polyamide comprising hexamethylenediamine, adipic acid and terephthalic acid is extremely effective as a crystallization accelerator for polyethylene terephthalate.
The first feature is that it was possible to obtain a sufficiently crystallized molded product by using an injection molding die at a temperature of not higher than 0 ° C. The action of an aliphatic polyamide should be called, as it were, a polymer crystal nucleating agent, and it is truly surprising that essentially different types of polymers act as crystallization accelerators for other types of polymers. The combination of polymers has never been known before.

Furthermore, in the present invention, the preferable properties that polyamide basically has are imparted, and the basic drawbacks of polyethylene terephthalate can be improved. In other words, the impact resistance and hydrolysis resistance have been improved, and the warpage of the molded product has been improved, and it has become possible to obtain injection molded products with extremely good balance of various physical properties.

Claims (1)

[Claims] 1. (A) Polyethylene terephthalate 60 to
Polyamide 2-40 consisting of 98% by weight and (B) hexamethylenediamine, adipic acid and terephthalic acid
An injection molding method for a polyethylene terephthalate resin composition, which comprises molding a resin composition consisting of wt% using a mold at 100 ° C or lower.