KR20020004215A - Polypropylene resin composition having good transparency and heat resistance - Google Patents

Abstract

PURPOSE: A polypropylene resin composition is provided, which is improved in the transparency and the heat resistance by using a polypropylene resin with high stereoregularity and a sorbitol-based nucleating agent. CONSTITUTION: The polypropylene resin composition comprises 100 parts by weight of a polypropylene resin with high stereoregularity which is such that a melting index is 0.3-3 g/10 min, a degree of molecular weight distribution measured by gel permeation chromatography is 5-12, and an index of stereoregularity by NMR according to the Pentad method is 96% or more; and 0.15-0.4 parts by weight of a sorbitol-based nucleating agent. Preferably the sorbitol-based nucleating agent is benzylidene sorbitol, methylbenzylidene sorbitol, ethylbenzylidene sorbitol, or 3,4-dimethylbenzylidene sorbitol.

Description

Polypropylene resin composition excellent in transparency and heat resistance {POLYPROPYLENE RESIN COMPOSITION HAVING GOOD TRANSPARENCY AND HEAT RESISTANCE}

The present invention relates to a polypropylene resin composition excellent in transparency and heat resistance, and more particularly, by adding a sorbitol-based nucleating agent to a high-stereoregular polypropylene resin, a resin composition having improved transparency and heat resistance as compared to a conventional polypropylene resin composition It is about.

Polypropylene resin is excellent in rigidity, chemical resistance, and moldability compared to other polyolefin-based materials, and thus has a wide industrial application range for automobile interior parts and home appliance parts. The reason why polypropylene resin is widely used as a polyolefin resin for injection molding is that polypropylene resin has superior rigidity, hardness, tensile strength, and heat resistance compared to polyethylene resin.

There are many techniques for increasing the rigidity and heat resistance of polypropylene resins for use in high temperature environments. In particular, in automobiles, electrical and electronic parts, and industrial material parts requiring high heat resistance, a method of reinforcing rigidity and heat resistance by mixing an inorganic filler with polypropylene resin has been proposed. In this regard, Japanese Patent Application Publication No. 53-64256, Some compositions have been improved by blending inorganic fillers and rubbers with polypropylene in SO 53-64257 and SO 57-55952, but problems such as poor appearance due to inorganic fillers and cost incurred due to specific gravity increase of materials And these methods make polypropylene resins opaque and therefore unsuitable for transparent product applications.

In order to solve this disadvantage, European Patent No. 562119 and Japanese Patent No. 5222078 have developed a resin composition which has improved rigidity and heat resistance by adding a phosphorus-based nucleating agent to a polypropylene resin without filling an inorganic material. Genie has a disadvantage in that heat resistance is inferior to inorganic filled polypropylene due to its low heat resistance.

In order to increase the transparency of polypropylene, a propylene-ethylene random copolymer has been developed in which a certain amount of ethylene is added and copolymerized when propylene is polymerized. However, propylene-ethylene random copolymer has a disadvantage in that it is not applicable to the application of continuous high temperature, such as iron, coffee maker, microwave oven due to the poor heat resistance.

It is an object of the present invention to improve the above problems, it is transparent and can be used at high temperature, high transparency regular heat resistance polypropylene resin that can be applied to heat-resistant electrical and electronic parts and home appliances applications and excellent vacuum formability It is to provide a composition.

The polypropylene resin composition of the present invention is characterized in that the sorbitol-based nucleating agent is added to the high-stereoregular polypropylene resin.

The polypropylene resin used in the present invention is a high-stereoregular polypropylene having a wide molecular weight distribution. The molecular weight distribution is 5-12 by gel permeation chromatography (GPC) method, and the stereoregularity index in nuclear magnetic resonance method is the pentaad method. It is preferable that it is 96% or more of the reference | standard, and melt index (MI) is 0.3-3 g / 10min (ASTM D1238, 230 degreeC).

If the molecular weight distribution of the polypropylene is less than 5, the extruder load rises and the amount of extrusion varies during the manufacture of the extrusion sheet for vacuum forming, and the high extrusion processing temperature is required. In addition, there is a risk of poor surface appearance due to poor flow, and there is a lot of residual stress due to high pressure on the final product, and when used at high temperature, the product is warped and distorted.

If the molecular weight distribution exceeds 12, it contains a lot of low molecular weight polypropylene resin in the final product, so it spreads to the surface when used at high temperature after molding the product, which greatly deteriorates the appearance.

If the stereoregularity index is less than 96%, the heat resistance of the polypropylene resin is lowered. The higher the stereoregularity index, the higher the heat resistance and the higher the mechanical strength. The special disadvantage of increasing the stereoscopic rule is that

none.

If the melt index of the polypropylene is less than 0.3g / 10 minutes, the productivity decreases due to poor moldability during extrusion molding, whereas if the melt index exceeds 3g / 10 minutes, the sheet droops during vacuum forming. The thickness deviation of the molded article occurs, and the value as a product is lowered.

Sorbitol-based nucleating agents used in the present invention are derivatives based on sorbitol, and include benzylidene sorbitol, methylbenzylidene sorbitol, ethylbenzylidene sorbitol, 3,4-dimethylbenzylidene sorbitol, and especially methylbenzylidene. Sorbitol and 3,4-dimethylbenzylidene sorbitol are preferred.

The amount of sorbitol-based nucleating agent added is preferably 0.15 to 0.4 parts by weight based on 100 parts by weight of polypropylene resin, and when the content is less than 0.15 parts by weight, it is difficult to obtain sufficient transparency, and when it exceeds 0.4 parts by weight, transparency is no longer improved.

To the polypropylene resin composition of the present invention, various additives such as antioxidants, heat stabilizers, weather stabilizers, antistatic agents, lubricants, pigments, dyes, and the like may be added within a range not departing from the features of the present invention.

There is no restriction | limiting in particular in the method of manufacturing the polypropylene resin composition of this invention, The method of manufacturing the polypropylene resin composition generally known can be used. Each of the above components can be freely selected and mixed according to a desired order. Usually, by adding necessary amounts of the above components and other additives, a kneader such as a kneader, a roll, a short-barrier mixer and a single or twin screw extruder are used. A kneading method can be used.

The present invention can be understood in more detail by the following examples, the following examples are only examples for illustrating the present invention and are not intended to limit the protection scope of the present invention.

Examples and Comparative Examples

The ingredients shown in Table 1 below were all added to the Gaigai PCM30 twin-screw kneading extruder at once and kneaded to prepare a polypropylene resin composition, which was then injected into Samsung Klockner FCM-110 (clamping force = 110 tons) to ASTM specifications. Specimens were prepared and evaluated for physical properties. Test conditions for injection and test properties are as follows. In addition, the physical property results are shown in [Table 1].

* Test Specimen

Injection molding machine: 110 tons (9.2oz)

Injection Specimen Type: ASTM No.4 Family (for property evaluation), 100x100x2mm specimen (Haze

For evaluation)

Feeding part temperature: 210 ℃

Cylinder and nozzle temperature: 240 ℃

Mold temperature: 60 ℃

Cooling time: 30 seconds

Injection Speed: 15mm / sec

Injection pressure: 85 bar

Measurement item: Measurement of physical properties of the specimen injected under the above conditions

Test conditions for each test property are as follows.

1) Melt Index

According to ASTM D1238, it measured at 2.16Kg load at 230 degreeC.

2) flexural rigidity

Measured according to ASTM D790

3) heat deflection temperature

It was measured under low load (4.6Kg) according to ASTM D648.

4) Haze

The transparency of the specimens was measured according to ASTM D1003. The lower the blur, the more transparent.

5) High temperature warpage evaluation

The resin composition was injected into a round disc shape having a diameter of 100 mm and a thickness of 1.7 mm to prepare a specimen, and then placed in an oven at 100 ° C. and 150 ° C. for 2 hours. This was again cooled to room temperature to evaluate the degree of warpage of the specimen. The degree of roughness was evaluated by placing the specimen on a flat table and measuring the height of the largest section from the table surface.

6) Evaluation of Mold Thickness Deviation

The resin composition was fabricated into a flat sheet having a thickness of 1.5 mm, the sheet was heated to a temperature of 280 ° C., and a cylindrical product having a diameter of 80 mm and a height of 100 mm was vacuum-molded to measure the thickness of the lowermost corner of the molded article.

1) Blur: The lower the blur, the more transparent.

2) High temperature warpage evaluation: O Good (no warpage), x defect (warpage occurrence, 1 ~ 2mm)

3) Thickness deviation of molded product: O Good (no warpage), X defect (When -20% difference from standard dimension occurs)

Description of each component used in Examples and Comparative Examples of Table 1 is as follows.

1) Polypropylene 1: Highly crystalline polypropylene homopolymer with a melt index (MI) of 0.5 g / 10 min (230 ° C.), nuclear magnetic resonance method pentaad method stereoregularity index of 97%, and molecular weight distribution of 8.0

2) Polypropylene 2: Polypropylene homopolymer with melt index (MI) of 10g / 10min (230 ℃), nuclear magnetic resonance method pentaad method stereoregularity index of 91% and molecular weight distribution of 4.5

3) Sorbitol-based nucleating agent: 3,4-dimethylbenzylidene sorbitol

4) Aluminum-based nucleating agent: aluminum hydroxydibutyl benzoate

As can be seen from the results of Table 1, Example 1 is superior in Comparative Example 1, which does not use the sorbitol-based nucleating agent and excellent in high temperature warpage evaluation due to the high rigidity and heat deformation temperature.

In Example 2, the polypropylene used compared to Comparative Example 2 has a high stereoregularity, so it is excellent in rigidity and heat deformation temperature, and has a high molecular weight (low melt index), so that the thickness variation of the vacuum molded article is excellent. Although the transparency of Example 2 and Comparative Example 2 is the same, Comparative Example 2 is distorted in the high temperature warpage evaluation. Therefore, the comparative example 2 is unsuitable for the use of the product used at high temperature.

In the case of Example 1 and Comparative Example 3, Example 1 has a higher transparency than Comparative Example 3 using an aluminum-based nucleating agent, and since the polypropylene used has high solid regularity, it has excellent rigidity and heat deformation temperature and high molecular weight. It has (low melt index), so the thickness variation of vacuum molded product is excellent. In addition, while Example 1 does not bend at a high temperature even at a similar heat deformation temperature, Comparative Example 3 was warped.

As can be seen in the above examples and comparative examples, the polypropylene resin composition prepared according to the present invention is excellent in vacuum formability and good heat resistance by using a high-stereoregular polypropylene resin having a wide molecular weight distribution, and at a high temperature. It does not cause warping even if used, so it is suitable for applications requiring transparency in microwave ovens, coffee makers, irons, etc., where such performance is required.

Claims (2)

Melting index of 0.3-3g / 10min, molecular weight distribution measured by gel permeation chromatography (GPC), 5-12, and stereoscopic rule of nuclear magnetic resonance method of 96% or higher based on pentaad method A polypropylene resin composition, wherein 0.15 to 0.4 parts by weight of a sorbitol-based nucleating agent is added to 100 parts by weight of a polypropylene resin. The polypropylene resin composition according to claim 1, wherein the sorbitol-based nucleating agent is benzylidene sorbitol, methylbenzylidene sorbitol, ethylbenzylidene sorbitol, or 3,4-dimethylbenzylidene sorbitol.