KR20020029215A - The polypropylene resin of excellent high melr-strength and their process - Google Patents

Abstract

PURPOSE: Provided are a polypropylene resin excellent in melt tension, which can be applied to a foam molding, a blow molding, and a heat molding and can be recycled, and a process for producing the polypropylene resin. CONSTITUTION: The polypropylene resin is produced by mixing 100pts.wt. of a crystalline polypropylene resin having a melt index (ASTM 1238, 230deg.C) of 0.1-50g/10min and a weight average molecular weight of more than 100,000g/mol, 0.05-10pts.wt. of a multi-functional monomer such as divinyl benzene and pentaerythritol triacrylate, and 0.005-5pts.wt. of an organic peroxide and then reaction-extruding. The crystalline polypropylene is a homopolymer of propylene or a block or heterogeneous copolymer of the propylene with C3-C15 alpha-olefin, wherein the alpha-olefin content is 0-50mol% per a mol of the propylene.

Description

The polypropylene resin of excellent high melr-strength and their process}

The present invention relates to a polypropylene resin having excellent foamability and a method for manufacturing the same, and more particularly, to a chip and a method for manufacturing the same, which have a significantly increased melt tension by introducing side chains into a polypropylene having a linear structure. The present invention relates to a polypropylene resin having a side branch and an increased melt tension by adding polyfunctional monomers and organic peroxides and reacting and extruding, and having excellent foamability and the like, and a method of manufacturing the same.

In general, polypropylene is a general purpose plastic having a relatively high strength and excellent mechanical properties compared to other resins, which is due to the crystal structure and the molecular structure of the polymer chain. Furthermore, homopolypropylene has excellent resistance to deformation at high temperature, has high tensile strength and surface rigidity, and copolypropylene with irregular or block copolymerization of ethylene or butylene increases impact strength depending on the application.

Polypropylene, on the other hand, has been difficult to foam compared to other plastic materials due to its weak melt tension due to its linear chain structure, which has shown limitations on foam production. If the melt tension is weak, as in the case of polypropylene, the cell walls separating the bubbles are not strong enough to overcome the tensile force and easily collapse and rupture. As a result, the foamed polypropylene product has a high content of collapsed cells and unsatisfactory control of the cell structure. In addition, in the case of vacuum molding or blow molding, sagging due to weak melt tension during heating of the sheet or preform was severe, and satisfactory formability was not obtained.

Therefore, in order to overcome this, various methods for increasing the melt tension of polypropylene have been proposed. The first method is the intermolecular crosslinking, which not only stabilizes the bubble growth during foaming through crosslinking, It can improve the resistance to thermal collapse. The three-dimensional network structure formed by the intrinsic bonding when crosslinking the polyolefin can improve important physical properties such as heat, abrasion, viscous deformation, chemical resistance, etc., and can also increase impact strength and tensile strength. At this time, the degree of crosslinking, distribution of crosslinking, crosslinking speed and the like all affect the expansion and physical properties of the foam. Crosslinking is affected by molecular structure, crosslinking method, time and temperature state. Optimum crosslinking is determined by the actual foam expansion experiments of a given process and production. When crosslinking is insufficient, the collapse of bubbles occurs, while excessive crosslinking limits the expansion of the foam.

On the other hand, in the crosslinking method, a crosslinking agent is added to a radical generator or made into a modified ethylenic resin in which an ethylenically unsaturated silane compound is grafted in the presence of a radical generator, followed by crosslinking in the presence of a silanol condensation catalyst and water vapor. The method of radically improving physical properties such as heat resistance, creep resistance, environmental stress resistance, and chemical resistance was introduced through water bridge. This crosslinking method has industrial value, such as a significantly reduced equipment cost and relatively easy crosslinking compared to the conventional method using an electron beam, and thus has been put into practical use in fields such as wire coating, pipes, films, and shrinking tubes.

Several methods have been attempted to increase the melt tension. Patent WO 94/26794, PolyBrasil, is a process for producing polypropylene with successively high melt tension, which is characterized by a high molecular weight by controlling different amounts of hydrogen in two different reactors. A method for producing 10 to 35% of polypropylene and 65 to 90% of low molecular weight polypropylene is presented. However, there is a drawback that the zero viscosity and the shear reduction phenomenon, which are evidence of the melt tension, have a similar behavior to that of the existing polypropylene resin.

As a technique of using a polyfunctional monomer as a crosslinking aid, organic peroxide and divinylbenzene are disclosed in Japanese Patent Publication No. 36-6195, organic peroxide and bismaleimide in Japanese Patent Publication No. 50-28546, and Japanese Patent Application Publication In 51-132253, organic peroxides and liquid polybutenes are used, US Pat. No. 3,227,698 uses organic peroxides and dinitroso compounds, and in British Patent No. 896,309, benzoquinonedioximes are used for crosslinking polypropylene. However, it has not been commercialized due to the lack of commercially sufficient degree of crosslinking.

On the other hand, Nojiri et al. Produced a foam by crosslinking polypropylene with triacrylate or trimethacrylate. After mixing the crosslinking agent and polypropylene in an extruder, the sheet was extruded to introduce crosslinking into polypropylene. Gamma rays were irradiated. This method has the disadvantage that continuous mass production is difficult.

The present invention is to solve the problems as described above, to increase the melt tension and to produce a polypropylene resin applicable to the process of foam molding, blow molding, thermoforming and the like, the existing invention is a melt tension Unlike crosslinking the polypropylene resin to increase the amount of side by introducing a side branch to increase the melt tension. Therefore, since the crosslinking is not made, the tension of the thermoplastic resin can be maintained as it is. To this end, the technical problem is to prepare a modified polypropylene resin through the reaction extrusion process of a polypropylene resin together with an organic peroxide as an initiator and a polyfunctional monomer as a reaction aid.

1 and 2 are graphs showing the elongation viscosity.

3 and 4 are graphs showing the composite viscosity

In the present invention, the melt index (ASTM D 1238, 230 ^° C) is 0.1 to 50 g / 10 minutes, 0.05 to 10 parts by weight of the multifunctional monomer, based on 100 parts by weight of the crystalline polypropylene resin having a weight average molecular weight of 100,000 g / mol or more, organic The present invention relates to a polypropylene resin having excellent melt tension obtained through a reaction extrusion process by mixing 0.005 to 5 parts by weight of peroxide, and a method for producing the same.

If the content of the polyfunctional monomer is less than 0.05% by weight, the cleavage of the polymer chain does not occur, and it is impossible to make a side branch. If the content of the polyfunctional monomer exceeds 10% by weight, the cleavage of the polymer chain is excessive, which causes a decrease in molecular weight. It becomes impossible to produce polypropylene resin.

In addition, when the content of the organic peroxide is out of the above range, the above problems occur.

Hereinafter, the present invention will be described in detail.

In the present invention, the term 'polypropylene' means a block or irregular copolymer with propylene homopolymer or other α-olefin having 3 to 15 carbon atoms. Examples of other α-olefins include 1-butene, 1-pentene, 1-hexene, and 1-octene. The amount of α-olefin copolymerized with propylene is from 0 to 50 mol% per mol of propylene.

In addition, the weight average molecular weight of 100,000g / mol or more, the melt index is 0.1 to 50g / 10 minutes (230 ^° C) is targeted.

Organic peroxides as initiators include benzoyl peroxide, di-t-butyl peroxide, dicumylperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2, 5-di (t-butylperoxy) hexane-3, butyl-4,4-bis (t-butyl peroxyvalerate), cumylhydroperoxite, lauroylperoxide, t-butylperoxyacetate, t- At least one compound selected from the group consisting of butyl peroxymethyl ethyl ketone peroxide, t-butyl cumyl peroxide and (t-butyl peroxy) -butylate is used.

As the polyfunctional monomer as a reaction aid, divinylbenzene, pentaerythritol triacrylate, trimetholpropane triacrylate, 1-6 hexanediol diacrylate, 1-4 butenediol diacrylate, and cyclohexyl methacrylate At least one compound selected from the group consisting of methyl acrylate, phenyl acrylate, benzyl acrylate and the like is used.

The above ingredients are mixed in a powder state and reacted through an extruder to produce a side branch. The extruder uses a twin screw extruder, and the temperature of the extruder is suitably 150 ^o C to 230 ^o C. If it is less than 150 ° C., the reaction does not proceed properly. Because.

Polypropylene resin excellent in the melt tension according to the present invention can be used in a variety of large products such as foam molding, vacuum molding, blow molding.

As shown in the following examples, the polypropylene resin having excellent melt tension according to the present invention exhibits enhanced reinforcement phenomena as compared to existing polypropylene chips when elongation viscosity is measured, and yielding phenomena appears in a low frequency region when compound viscosity is measured. .

Hereinafter, the present invention will be described by way of examples, but the present invention should not be considered as being limited by these examples.

In the following examples, melt strength, complex viscosity, and extensional viscosity were measured by the following method.

1) Melt Tension

Melt strength of polypropylene was measured using a capillary rheometer manufactured by Toyo Seiki Co., Ltd. (Japan), and the polypropylene was discharged downward by using a piston after maintaining 230 ^° C. for 6 minutes in the barrel. The speed of the piston was 20mm / min and the diameter of the circular die was 2.095mm. At the lower end of the capillary rheometer, a pulling device and a device for measuring the pulling force were installed to measure the force while pulling at a constant speed. At this time, the pulling speed was maintained at 3.14m / min.

2) Complex Viscosity

The polypropylene chip was maintained at a temperature of 250 ^° C. for 10 minutes using a hot press to prepare a circular specimen having a thickness of 2 mm. Compound viscosity was measured using RRES's Advanced Rheomteric Extension System (ARES) and measured at a frequency of 0.1-500 at a temperature of 250 ^° C.

3) Extensional viscosity

Circular polypropylene specimens were fabricated using an extruder equipped with a circular die with a diameter of 2 mm. The elongation viscosity was measured using Meissner type elongation viscosities and maintained at 190 ^o C for 3 minutes using silicone oil. After that, the stretching viscosity was increased by pulling at a rate of 0.1 / min.

Example 1

2,5-dimethyl-2,5-di (t-butylperoxy) hexane 2,000 as an organic peroxide in a polypropylene resin with a melt index of 0.4 g / 10 min (230 ^o C, 2.16 kgf) and 10% ethylene content 10,000 ppm of polyvinyl and polyfunctional monomer divinyl and 1,500 ppm of phenolic antioxidant and phosphite antioxidant, 700 ppm of calcium stearate with halogen absorber and melt mixed at extruder at 180-230 ℃ with pellet Mad Melt strength, compound viscosity, and elongation viscosity were measured by the above method using the pellets, and the results are shown in Table 1, FIGS. 1 and 3.

Example 2

2,5-dimethyl-2,5-di (t-butylperoxy) hexane 3,000 as an organic peroxide in a polypropylene resin with a melt index of 0.4 g / 10 min (230 ^o C, 2.16 kgf) and 10% ethylene content 15,000 ppm of divinyl ppm, polyfunctional monomer, 1,500 ppm of phenolic antioxidant and phosphite antioxidant, and 700 ppm of calcium stearate with halogen absorber were melt mixed at an extruder at 180-230 ° C for pellets. Mad Melt strength, compound viscosity, and elongation viscosity were measured by the above method using the pellets, and the results are shown in Tables 1, 1, and 3.

Example 3

Polypropylene resin with a melt index of 0.4 g / 10 min (230 ^° C., 2.16 kgf), 2,000 ppm benzoyl peroxide as an organic peroxide, and 15,000 ppm trimetholol propane triacrylate as an organic peroxide. And 1,500 ppm of phenolic antioxidant and phosphite antioxidant and 700 ppm of calcium stearate were mixed together with a halogen absorber and melt-blended at 180 to 230 ° C. with an extruder for pelletization. The pellets were used to measure melt strength, compound viscosity, and elongation viscosity by the above method, and the results are shown in Tables 1, 2, and 4.

Example 4

Melting index 0.4g / 10min (230 ^° C, 2.16kgf), 10% ethylene content, polypropylene resin, 3,000 ppm of benzoyl peroxide as organic peroxide, 15,000 ppm of trimethylolpropane triacrylate as a polyfunctional monomer And 1,500 ppm of phenolic antioxidant and phosphite antioxidant and 700 ppm of calcium stearate were mixed together with a halogen absorber and melt-blended at 180 to 230 ° C. with an extruder for pelletization. The pellets were used to measure melt strength, compound viscosity, and elongation viscosity by the above method, and the results are shown in Tables 1, 2, and 4.

Comparative Example 1

Polypropylene resin with a melt index of 0.4 g / 10 min (230 ^o C, 2.16 kgf), 1,500 ppm of phenolic antioxidant and phosphite antioxidant, and 700 ppm of calcium stearate with halogen absorber After mixing, the mixture was melt mixed at 180 to 230 ° C. with an extruder and pelletized. Melt strength, composite viscosity, and elongation viscosity were measured by the above method using the pellets, and the results are shown in Table 1 and FIGS. 1, 2, 3, and 4.

Melt Strength Measurement Results Melt Index (g / 10min) Ethylene (%) Organic Peroxide (%) Polyfunctional Monomer (%) Melt strength [g] Example 1 (# 1) 0.4 10 2,5-dimethyl-2,5-di (t-butylperoxy) hexane0.2 Divinylbenzene1.0 14.5 Example 2 (# 2) 0.4 10 2,5-dimethyl-2,5-di (t-butylperoxy) hexane0.3 Divinylbenzene1.5 12.8 Example 3 (# 3) 0.4 10 Benzoyl Peroxide 0.2 Trimetholpropane triacrylate 1.5 12.9 Example 4 (# 4) 0.4 10 Benzoyl peroxide 0.3 Trimetholpropane triacrylate 1.5 12.6 Comparative Example 1 (# 5) 0.4 10 - - 5.5

The polypropylene resin made by the present invention can be applied to existing impossible processes such as foaming process, vacuum molding process, blow molding process by increasing the melt tension by more than 2 times compared to the existing resin by introducing a side branch. In addition, since the crosslinking is not a method, the properties of the thermoplastic resin can be maintained and recycled.

Claims (5)

0.05-10 parts by weight of polyfunctional monomer and 0.005-by weight of organic peroxide to 100 parts by weight of the crystalline polypropylene resin having a melt index (ASTM D 1238, 230 ^° C) of 0.1-50 g / 10 min, a weight average molecular weight of 100,000 g / mol or more. A method for producing a polypropylene resin having excellent melt tension, comprising 5 parts by weight of a reaction extrusion process. The melt according to claim 1, wherein the crystalline polypropylene is a homopolymer of propylene or a block or an irregular copolymer with 3 to 15 carbon atoms of an olefin, and has a content of 0 to 50 mol% per mole of propylene. Method for producing a polypropylene resin excellent in tension. The organic peroxide of claim 1, wherein the organic peroxide is benzoyl peroxido, di-t-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5- Dimethyl-2,5-di (t-butylperoxy) hexane-3, butyl-4,4-bis (t-butyl peroxyvalerate), cumylhydroperoxite, lauroyl peroxide, t-butylperoxy Polypropylene resin having excellent melt tension, characterized in that at least one compound selected from the group consisting of acetate, t-butylperoxymethylethylketone peroxide, t-butyl cumylperoxide and (t-butylperoxy) -butylate Manufacturing method. The method of claim 1, wherein the polyfunctional monomer is divinylbenzene, pentaerythritol triacrylate, trimetholpropane triacrylate, 1-6 hexanediol diacrylate, 1-4 butenediol diacrylate, cyclohexyl meta A method for producing a polypropylene resin having excellent melt tension, characterized in that at least one compound selected from the group consisting of acrylate, methyl acrylate, phenyl acrylate, benzyl acrylate and the like. The polypropylene resin produced by the method of Claim 1.