JPH0321569B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing crosslinked polyolefin molded products, and more specifically, it has excellent workability and safety, is economical, and can easily produce beautiful and high-quality molded products with complex shapes. The present invention relates to a method for producing a crosslinked polyolefin molded article that can be obtained. Polyolefin molded articles generally have problems in heat resistance, impact resistance, etc., and thus polyolefins have been crosslinked by various methods for the purpose of improving these physical properties. The most widely known method is to add an organic peroxide and heat it, but in this method, the polyolefin is kneaded and molded at a temperature close to the thermal decomposition temperature of the organic peroxide, so it is rapidly heated. Problems due to crosslinking are likely to occur, and extremely strict temperature control is required. Furthermore, in recent years, methods using ionizing radiation such as gamma rays and electron beams have been proposed. However, this method has problems in that the equipment used is expensive, handling is not common, and there is a high risk to the human body, and furthermore, it is difficult to apply to molded products of complicated shapes. Thus, to date, there is still no known method for crosslinking and molding polyolefins with good workability, safety, and simple equipment. Therefore, the present inventors have conducted extensive research in order to develop an excellent method that overcomes the drawbacks of the above-mentioned conventional techniques. As a result, it was discovered that the object could be achieved by first treating polyolefin with ozone, then adding a crosslinking aid and molding under heat, and completed the present invention. That is, the present invention provides a method for producing a crosslinked polyolefin molded article, which comprises bringing polyolefin into contact with ozone, then adding a crosslinking aid, and then hot molding. The polyolefin used in the method of the present invention is not particularly limited, and various types can be used. Specific examples include medium- and low-density polyethylene, high-density polyethylene, polypropylene, copolymers containing ethylene or propylene as a main component, and mixtures thereof. In the method of the present invention, the polyolefin as described above is first brought into contact with ozone to perform ozone treatment.
This ozone treatment activates the polyolefin,
This is carried out so that the crosslinking reaction proceeds smoothly during the subsequent hot molding, and the processing conditions are not particularly limited. In short, it is sufficient to carry out the process while the polyolefin is in sufficient contact with ozone. Specifically, the ozone-containing gas is placed in the container in which the polyolefin is supplied, and the ozone concentration is usually 0.5 to 20% by volume, preferably 1 to 5% by volume. It is sufficient to introduce gas in an amount of about % by volume and allow contact at room temperature to 80° C. for about 0.5 to 8 hours. This contact is usually carried out by directly bringing the ozone-containing gas into contact with the polyolefin powder, but it can also be carried out in water or various organic solvents. Further, as an ozone source, a normal ozone generator may be used. In the method of the present invention, a crosslinking aid is then added to the polyolefin activated by ozone treatment. Since this crosslinking aid promotes the crosslinking reaction of the polyolefin, it is preferable to sufficiently knead it with the polyolefin after addition to uniformly disperse it. The crosslinking aid that can be used here is not particularly limited, and may be appropriately selected depending on the type of polyolefin used. Specific examples include divinylbenzene, triallyl cyanurate, vinyltriethoxysilane, triallyl isocyanurate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, diallyl phthalate, or mixtures thereof. The amount of the crosslinking aid added varies depending on various conditions and cannot be determined unambiguously, but it is usually 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight, per 100 parts by weight of the polyolefin. Should be. The above-mentioned crosslinking aid is added to the ozone-treated polyolefin and kneaded by a commonly used kneader, such as a twin-roll kneader, a Banbury mixer, or the like. In the method of the present invention, after adding a crosslinking aid to the ozonated polyolefin and thoroughly mixing it,
Hot mold into desired shape. Through this hot molding, the crosslinking reaction of the polyolefin progresses, and at the same time it is molded into a desired shape, yielding a crosslinked polyolefin product. Here, stimulation such as heat and pressure is applied to the polyolefin activated by ozone treatment in the presence of a crosslinking aid, so that the crosslinking reaction proceeds in parallel with the molding. The above hot forming method may be appropriately determined depending on the type, shape, etc. of the desired molded product, and is not particularly limited. Specifically, extrusion molding, injection molding, blow molding, press molding, foam molding, etc. can be mentioned. Further, the temperature during hot molding should be determined according to various conditions, but when the molding temperature is relatively low, it is preferable to perform an annealing treatment after molding to complete the crosslinking reaction. The conditions for this aryling treatment may be determined depending on the progress of the crosslinking reaction of the polyolefin, but it is usually carried out at 90 to 120°C for about 0.5 to 15 hours. According to the method of the present invention, the crosslinking of the polyolefin proceeds relatively slowly in parallel with the molding, so that it is excellent in safety and workability, and at the same time, it is possible to manufacture molded products with complex shapes.
Furthermore, since the polyolefin can be crosslinked and molded using simple equipment, it is an extremely advantageous method economically. The cross-linked polyolefin molded products obtained in this way have excellent heat resistance, cleaving resistance, environmental stress fracture resistance, abrasion resistance, low temperature properties, memory effect, etc., and can be used as wire coatings, pipes, sheets, films, etc. Suitable for industrial materials, machinery, electrical parts, etc. Next, the present invention will be explained in more detail with reference to Examples. Example 1 High-density polyethylene (manufactured by Idemitsu Petrochemical Co., Ltd.: Density
0.954g/cm ³ , melt index (MI) 0.9g/
10 minutes) was placed in a container, and a gas with an ozone content of 2.1% by volume from an ozone generator was continuously introduced into the container, and contact treatment was performed at 45° C. for 6 hours.
Next, this ozone-treated high-density polyethylene
2 parts by weight of divinylbenzene was added to 100 parts by weight, and the mixture was kneaded at 150°C for 7 minutes using twin-screw heated rolls. Next, this kneaded product was press-molded at 190°C to obtain a sheet with a wall thickness of 1 mm. Take a sample piece from the obtained sheet and place it at 125
The sample was immersed in paraxylene at ℃ for 8 hours, the remaining gel was removed, dried, and the basis weight was determined to determine the insoluble gel fraction. The results are shown in Table 1. Example 2 Example 1 except that the ozone treatment time was 4 hours and 2 parts by weight of triallyl cyanurate was used instead of divinylbenzene.
High-density polyethylene was crosslinked in the same manner. The results regarding the insoluble gel fraction are shown in Table 1. Example 3 High-density polyethylene was crosslinked in the same manner as in Example 1 except that 4 parts by weight of vinyltriethoxysilane and 0.05 parts by weight of dibutyltin dilaurate were added instead of divinylbenzene. The results regarding the insoluble gel fraction are
Shown in the table. Example 4 Low-density polyethylene powder (manufactured by Toyo Soda Co., Ltd., trade name Petrocene 170) was placed in a container, and a gas containing 2.1% ozone by volume was continuously introduced into the container to form low-density polyethylene at 45°C. Contact treatment was carried out for 4 hours. Next, 2 parts by weight of triallyl cyanurate was added to 100 parts by weight of ozone-treated low-density polyethylene, and the mixture was heated at 140°C using a biaxial heating roll.
The mixture was kneaded for 7 minutes. Next, this kneaded product was press-molded at 160°C to obtain a sheet with a wall thickness of 1 mm. Take out a sample piece from the obtained sheet and
It was immersed in xylene at 105°C for 8 hours, the remaining gel content was removed, dried, and the basis weight was determined to determine the insoluble gel fraction. The results are shown in Table 1. Example 5 Polypropylene (manufactured by Idemitsu Petrochemical Co., Ltd.: density 0.90
g/cm ³ , MI 2.5 g/10 minutes) was placed in a container, and a gas containing 2.1% by volume of ozone was continuously introduced into the container, and contact treatment was carried out for 2 hours. Then, for 100 parts by weight of ozone-treated polypropylene,
Two parts by weight of divinylbenzene were added, and the mixture was kneaded at 200°C for 10 minutes using a Labo Plus Mill. Next, this kneaded material was press-molded at 220℃, and the wall thickness was 1 mm.
Got a sheet. Take out a sample piece from the obtained sheet and
It was immersed in decalin at 135°C for 8 hours, the remaining gel content was taken out, dried, and the basis weight was determined to determine the insoluble gel fraction. The results are shown in Table 1. Comparative Example 1 2 parts by weight of dicumyl peroxide was added to 100 parts by weight of the same high-density polyethylene as in Example 1, and the mixture was kneaded at 150°C with a twin-axial hot roll.
Three minutes after the start of kneading, the high-density polyethylene became crosslinked and became impossible to knead. The insoluble gel fraction was determined in the same manner as in Example 1 for this crosslinked high-density polyethylene strip. The results are shown in Table 1. 【table】

Claims (1)

[Scope of Claims] 1. A method for producing a crosslinked polyolefin molded article, which comprises bringing polyolefin into contact with ozone, then adding a crosslinking aid, and then hot molding. 2. The method according to claim 1, wherein the crosslinking auxiliary agent is divinylbenzene, triallyl cyanurate, vinyltriethoxysilane, triallyl isocyanurate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, or diallyl phthalate.