CN1523052A - Cross-linked polyethylene special material for rotational molding - Google Patents

Abstract

The invention relates to a special material for cross-linked polyethylene for rotational molding, which comprises the following components: (based on the total weight of the linear low density polyethylene and the low density polyethylene) a. linear low density polyethylene, 70-90%; B. 10-30% of low-density polyethylene; C. 0.5-5% of cross-linking agent; D. 0.1 to 1 percent of antioxidant. The invention also relates to a preparation method of the special material, which comprises the step of melting and mixing the special material composition in an open mill or a double-screw extruder, wherein the blending temperature is 130-170 ℃, and the special material for polyethylene can be prepared. The rotational molding product prepared by the special material has good processing performance, and has super-group impact strength, thermal creep resistance, low-temperature toughness, good permeability resistance, chemical resistance and the like.

Description

Cross-linked polyethylene special material for rotational molding

Technical field

The invention relates to a special cross-linked polyethylene material for rotational molding.

Background technique

Rotational molding is one of the methods of forming large and medium-sized products. This process originated in the United States in the 1940s. Due to various reasons, it has developed slowly and is limited to the processing of a few plastic products. In recent years, due to the development of plastics and their powdering, the gradual expansion of the application field of plastics, and the superiority of this process, it is developing rapidly. At present, the proportion of various types of rotationally molded polyethylene materials in foreign countries is roughly: 65% for linear low-density polyethylene (LLDPE), 20% for cross-linked polyethylene (XHDPE), 10% for high-density polyethylene (HDPE), and 10% for low-density polyethylene (LDPE). Polyethylene (LDPE) is 5%. In the late 1970s, linear low-density polyethylene (LLDPE) began to enter the field of rotational molding. Linear polyethylene itself has the characteristics that are particularly suitable for rotational molding: 1. Good rotational molding performance and short molding cycle; 2. Good stress crack resistance; 3. Good impact resistance; 4. Good rigidity; 5. Linear polyethylene rotomoulding powder is easy to obtain. Due to the various advantages of LLDPE in the rotational molding process and its products, it has been considered as a plastic with good development prospects in the rotational molding field. Now, the application of LLDPE in rotomolding has been very impressive. According to the information, LLDPE rotomolding products have accounted for 65% of all polyethylene rotomolding products in the United States. At present, 90% of traditional high-density polyethylene has turned to LLDPE. However, LLDPE still has defects such as poor processability, thermal creep resistance, low temperature impact resistance, and swelling resistance, which undoubtedly limit the application range of LLDPE.

Contents of invention

The purpose of the present invention is to overcome the above-mentioned shortcoming of prior art, provide a kind of cross-linked polyethylene (LLDPE) special material for rotational molding.

The cross-linked polyethylene special material for rotational molding provided by the present invention contains the following components: (based on the total weight of linear low density polyethylene and low density polyethylene)

A. Linear low density polyethylene, 70--90%;

B. Low-density polyethylene, 10--30%;

C, crosslinking agent, 0.5-5%;

D. Antioxidant, 0.1-1%.

The crosslinking agent in the composition provided by the invention can be organic peroxide, as dicumyl peroxide (DCP), 2,5 dimethyl-2,5 di-tert-butyl hexane (two 2,5 ), di-tert-butyl peroxide, etc.; the antioxidant can be tetrakis {-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate} pentaerythritol ester (antioxidant 1010) or thiodi Dilauryl propionate (DLTP), etc.

The present invention also provides a preparation method of special cross-linked polyethylene material, the method comprising: melting and mixing the special material in an open mill or a twin-screw extruder, and the blending temperature is 130-170°C, to produce Get the polyethylene special material.

The mechanism of the present invention is that cross-linking occurs during the preparation and molding process of the special material of the present invention, thereby forming a network structure. Cross-linked rotomolding is a kind of peroxide liquid-phase cross-linking. Cross-linking is achieved through the C-C bond formed by the alkyl group. After heating peroxidation (ROOR), active free radicals are formed. The cross-linking reaction formula is as follows:

ROOR-2RO

The cross-linking reaction occurs above the melting point of the material, and the formation of gel after cross-linking restricts the movement of the molecular chains, so that the molecular chains cannot be fully, rapidly and regularly arranged, and the resulting crystals are less perfect, which is harmful to The crystallization behavior of the material has a great influence, followed by a decrease in the density of the material, and the product has more ideal properties. The blending of two kinds of polyethylene can produce polyethylene material with moderate softness and hardness and excellent processability. So as to adapt to a wider range of uses.

The special material has good fluidity, can withstand high temperature heating in the air, and has good rotational molding performance. The rotomolded products prepared with this material have superior impact strength, thermal creep resistance and low temperature toughness, good permeability resistance and chemical resistance, etc. The above-mentioned excellent properties of cross-linked polyethylene products enable them to be used in many fields where ordinary polyethylene products cannot be applied or are not applicable, such as fuel tanks, chemical containers, trash cans, and industrial battery cases.

Detailed ways

Example 1

formula:

LLDPE 7042 70 kg

LDPE 1F7A 30 kg

Dicumyl peroxide 4.5 kg

Antioxidant 1010 500g

Preparation: Mix the raw materials prepared according to the formula evenly in a high-speed mixer, and then blend on a double-roll mill, and the blending temperature is 130-140°C. The next piece was crushed.

Example 2

formula:

LLDPE 7042 90 kg

LDPE 1F7A 10 kg

2,5 dimethyl-2,5 di-tert-butyl hexane 1 kg

Dilauryl Thiodipropionate 900g

Preparation: The method is the same as the preparation method of Example 1.

Claims (5)

1, a kind of rotational moulding cross-linked polyethylene special material contains following component: (in the gross weight of linear low density polyethylene and new LDPE (film grade))

A, linear low density polyethylene, 70-90%;

B, new LDPE (film grade), 10-30%;

C, linking agent, 0.5-5%;

D, oxidation inhibitor, 0.1-1%.

2, PP Pipe Compound according to claim 1 is characterized in that: with this PP Pipe Compound melting mixing in mill or twin screw extruder, blending temperature is 130-170 ℃.

3, PP Pipe Compound according to claim 1 is characterized in that: linking agent wherein is an organo-peroxide.

4, PP Pipe Compound according to claim 2 is characterized in that: organo-peroxide wherein is one of dicumyl peroxide, 2,5 dimethyl-2,5 di-t-butyl hexane and ditertiary butyl peroxide.

5, according to according to the described PP Pipe Compound of claim 1, it is characterized in that oxidation inhibitor wherein is four { (3, the 5-di-tert-butyl-hydroxy phenyl) propionic acid } pentaerythritol ester or Tyox B.