JPH062826B2 - Method for producing polypropylene resin molded body - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a polypropylene resin molded body.

More specifically, the present invention relates to a method for producing a polypropylene resin molded body having excellent mechanical properties such as rigidity and temperature characteristics such as heat resistance and having high hardness.

[Prior Art and Problems Thereof] In general, polypropylene has a light specific gravity and is excellent in rigidity, chemical resistance, moldability and the like, and is therefore widely used in fields such as containers and packaging materials.

However, there is a drawback that the impact resistance at low temperature is poor.

In order to improve this drawback, an improved method of copolymerizing with ethylene to introduce an ethylene component into the molecular chain, and an improved property of blending polypropylene with rubber such as EPR are adopted.
The propylene polymer and the propylene polymer composition obtained by such an improved method are widely used in the field of industrial materials such as automobile parts such as bumpers and home electric appliances.

However, depending on the application, other properties should be emphasized together with rigidity, chemical resistance, moldability and impact resistance at low temperature, or these properties should be less important but other properties should be emphasized. Sometimes. For example, when excellent heat resistance and high hardness are required, the propylene polymer or the propylene polymer composition may be polystyrene, A
Inferior to BS resin. Therefore, a propylene polymer or a propylene polymer composition cannot be used as a material for producing a molded product which is required to have excellent heat resistance and high hardness. If you dare to use a propylene polymer or propylene polymer composition,
In order to satisfy the above-mentioned various properties, a molded product having a meat pressure must be formed. This prevents thinning of the molded product and increases the cost of the molded product. That is, the application of the propylene polymer or propylin polymer composition cannot be expanded.

If propylene polymer or propylene polymer composition has excellent rigidity, chemical resistance, moldability, impact resistance at low temperature,
As long as it has heat resistance and hardness, such a propylene polymer or a propylene polymer composition can be expanded in applications as a substitute for polystyrene or ABS resin. Moreover, since a thin molded product can be finished, resource saving and cost reduction can be expected.

Conventionally, in order to meet the above-mentioned demand, a method of heat-treating a polypropylene resin molded product containing EPR or an inorganic filler has been proposed (JP-A-51-47947 and JP-A-56-847).
(See Publication 28).

However, the heating temperature range in the examples in the above method is 140 ° C. or less, and it is the actual situation that a polypropylene resin molded body having sufficiently large rigidity, heat resistance and hardness to withstand practical use has not been obtained. .

[Object of the Invention] An object of the present invention is to provide a method for producing a polypropylene resin molded article having excellent mechanical properties such as rigidity and temperature characteristics such as heat resistance and having a large hardness.

Another object of the present invention is to provide a method capable of easily producing a polypropylene resin molded product excellent in rigidity even in mechanical properties by blending a specific additive.

[Means for Achieving the Object] The outline of the present invention for achieving the object is a polypropylene resin and a nucleating agent blended in a proportion of 0.005 to 1 part by weight based on 100 parts by weight of the polypropylene resin. An unoriented molding pair formed by molding a composition containing
Within the temperature range of 5 to 170 ° C., the melting point of the composition ±
It is a method for producing a polypropylene resin molding pair, characterized in that heat treatment is performed in a temperature range of 4 ° C.

Examples of the polypropylene resin include a propylene homopolymer pair, a propylene random copolymer obtained by copolymerizing propylene and an α-olefin other than propylene, and a copolymer of propylene and an α-olefin other than propylene by a multistage polymerization method or the like. So-called propylene block copolymers obtained by polymerization, as well as mixtures thereof can be used.

In the present invention, the propylene homopolymer does not mean only a polymer consisting of polypropylene, but contains a very small amount of α-olefin other than propylene as a monomer unit, for example, about 3% by weight. .Alpha.-olefin as a monomer unit thereof may be incorporated in the polypropylene main chain, or may be in polyethylene blended with polypropylene.

Among the various polypropylene resins mentioned above, the melting point is 160 to 1
It is preferably 65 ° C.

Further, among polypropylene resins having a melting point in the above range, propylene homopolymer and so-called propylene block copolymer are preferable.

Furthermore, among propylene homopolymers having a melting point in the above range, the intrinsic viscosity [η] is 1.0 to 4.0 dl / g, and the isotactic pentad fraction [I] is the following formula [I] ≧ -1.02 [ Propylene homopolymer satisfying η] +96.0 is preferable.

The propylene homopolymer itself satisfying the intrinsic viscosity [η] and the isotactic pentad fraction [I] is
It can be easily produced by adopting a known polymerization method such as a slurry polymerization method, a solution polymerization method, a gas phase polymerization method, a liquid phase polymerization method using an olefin monomer as a medium in the presence of a known stereoregular catalyst. be able to. Such polymerization methods are known and will not be described in detail here. However, for the intrinsic viscosity [η] of propylene homopolymer, add a molecular weight regulator such as hydrogen to the polymerization reaction system, and for the isotactic pentad fraction [I], the type of cocatalyst and polymerization A propylene homopolymer satisfying the intrinsic viscosity [η] and the isotactic pentad fraction [I] can be obtained by appropriately selecting the conditions and the like. Incidentally, the polymerization conditions for producing the polypropylene homopolymer having the intrinsic viscosity [η] and the isotactic pentad fraction [I] are as follows:
In such various polymerization methods, it is pointed out as an example that it is preferable to adjust the temperature during the polymerization to 0 to 150 ° C. and the pressure during the polymerization to 0.001 to 50 kg / cm ² .

Here, the intrinsic viscosity [η] can be measured in tetralin heated to 135 ° C.

In addition, the isotactic pentad fraction [I] is the ray. Macromolecules, 6 , 925 (1973) by A. Zambelli et al. [Mac Sakao molecules, 6,925 (19
73)], and is the isotactic fraction in pentad units in the molecular chain of polypropylene measured using ¹³ C-NMR. In other words, the isotactic pentad fraction is the fraction of propylene monomer units in which five propylene monomer units are continuously meso-bonded. However, regarding the attribution of peaks, Macromolecules, 8 , 687 (1975) [Macromolecules, 8 , 687, (1
975)] and the corrected version of the above document. Specifically, the isotactic pentad unit can be measured by the intensity fraction of the mmmm peak in all the absorption peaks in the methyl carbon region of the ¹³ C-NMR spectrum.

The value of the isotactic pentad fraction [I] is the value of the obtained crystalline polymer as it is, and is not the value of the polymer after extraction, fractionation and the like.

Among the so-called propylene block copolymers having a melting point of 160 to 165 ° C, the following can be mentioned as preferable ones.

That is, it contains (a) an α-olefin other than propylene as a monomer unit in an amount of 2% by weight or less and has an intrinsic viscosity [η] of 0.9 to 4.0 dl / g and a propylene homopolymer and / or a propylene copolymer [ The component (a). ] 55 to 95% by weight, and (b) 15 to 80% by weight of α-olefin other than propylene as a monomer unit
And the intrinsic viscosity [η] is 2 to 10 dl / g as the propylene copolymer [component (b)]. ] It is a polypropylene composition consisting of 45 to 5% by weight.

The polypropylene composition indicated as a preferred polypropylene resin contains at least the above-mentioned component (a) and component (b).

Examples of the method for producing this polypropylene composition include known methods such as a method of kneading the components (a) and (b) obtained by separate production, and a multi-step polymerization method such as a two-step polymerization or a three-step polymerization method. To be Above all. A two-stage polymerization method using a stereoregular catalyst is preferred.

This two-stage polymerization method is performed as follows.

The stereoregular catalyst used for polymerization is a catalyst generally used in stereoregular polymerization reaction of ethylene, propylene, etc., and is usually a catalyst prepared from at least a transition metal halide and an organoaluminum compound. .
Here, the transition metal halide is preferably a titanium halide, and examples thereof include titanium tetrachloride and titanium trichloride. And titanium trichloride is especially suitable.
Examples of tatin trichloride include titanium tetrachloride reduced by various methods; those activated by a treatment such as ball mill treatment and / or solvent washing; titanium trichloride or titanium dichloride eutectic (for example, , TiCl ₃
+ 1 / 3AlCl ₃ ) further co-ground with amine, ether, ester, sulfur, halogen derivative, organic or inorganic nitrogen compound or phosphorus compound, etc .; precipitated from liquid titanium trichloride in the presence of ether compound Examples thereof include those obtained by the method described in JP-B-53-3356. It is also possible to use a titanium halide supported on a magnesium compound.

Examples of the organoaluminum compound include the following formula AlR _m X
_3-m (wherein, R represents an alkyl group, an alkoxy group or an aryl group having 1 to 10 carbon atoms, X represents a halogen atom, and m represents a value of 0 <m ≦ 3). Compounds are preferred.

Specifically, for example, triethyl aluminum, triisobutyl aluminum, tri-n-propylene aluminum, diethyl aluminum monochloride, diethyl aluminum monobromide, diethyl aluminum monoiodide, diethyl aluminum monoethoxide, diisobutyl aluminum monoisobute. Tokiside,
Examples thereof include diisobutylaluminum mohydride, diisobutylaluminium monohydride, ethylaluminum sesquichloride, and ethylaluminum dichloride, and one or more of these can be used.

In these catalyst components, usually, 1 mol of the transition metal halide and 1 to 100 mol of the organoaluminum compound can be mixed and used. Alternatively, various electron donating compounds may be used as the third component to improve the catalytic performance.

Such a stereoregular catalyst is used at each stage of the polymerization reaction in the amount and the combination of each component that are usually used.

As the polymerization method, a known method can be applied,
For example, slurry polymerization, solution polymerization, gas phase polymerization, liquid phase polymerization using α-olefin such as propylene and ethylene as a medium can be mentioned.

When the polypropylene composition in which ethylene is selected as the α-olefin other than propylene is produced by a two-stage polymerization method, in the first stage, a propylene homopolymer in which the content of ethylene units in the polymer is 2% by weight or less and And / or propylene-ethylene copolymer is controlled so as to form 55 to 95% by weight, preferably 60 to 92% by weight of the total polymer.

When a propylene-ethylene copolymer having an ethylene unit content of more than 2% by weight in the first stage is used, the rigidity of the resulting composition may be significantly reduced.

In the second stage, ethylene is newly fed into the reactor in which the propylene homopolymer and / or propylene-ethylene copolymer obtained in the first stage polymerization reaction is present, or ethylene and propylene are newly supplied, The propylene-ethylene copolymer containing 15 to 80% by weight, preferably 20 to 70% by weight of ethylene unit causes the second stage polymerization reaction to occur by setting the predetermined polymerization conditions in the reactor. 5 to 45% by weight of polymer, preferably 8 to 40% by weight
Manage to generate. As a result, a suitable polypropylene composition is obtained in the present invention.

As the α-olefin other than propylene, in addition to the ethylene, butene-1, hexene-1, octene-1
Such as linear monoolefins, branched monoolefins such as 4-methyl-pentene-1, and dienes such as butadiene,
It can be used in the same manner as the ethylene.

In order to obtain a polypropylene composition having preferable physical properties,
As the other α-olefin, ethylene and butene-1 are preferable.

In a preferred polypropylene composition, in the component (a), the content of α-olefin other than propylene as a monomer unit is 2% by weight or less, and the intrinsic viscosity [η] is 0.9 to 4.0 dl / g, preferably Is 1.0 to 3.5
dl / g, and the blending ratio in the polypropylene composition is 55
~ 95% by weight, in particular 60-92% by weight, and
In the component (b), the content of α-olefin other than propylene as a monomer unit is 15 to 80% by weight, particularly 20 to 70% by weight, and the intrinsic viscosity [η] is 2 to
10 dl / g, particularly 2.5 to 8 dl / g, and the blending ratio in the polypropylene composition is 45 to 5% by weight, especially 40 to 8
% By weight.

Here, if the content of the α-olefin in the component (a) is more than 2% by weight, rigidity, heat resistance, hardness and the like may decrease.

When the intrinsic viscosity [η] of the component (a) is less than 0.9 bl / g, the impact resistance of the unblended molded product (hereinafter, referred to as polypropylene resin molded product) of the present invention is lowered. And the intrinsic viscosity [η] is 4.0d.
If it is larger than 1 / g, the number and the heat resistance may decrease.

Furthermore, if the proportion of the component (a) in the polypropylene composition is less than 55% by weight, the rigidity and heat resistance of the polypropylene resin molded body may decrease.
When the proportion of the component (a) is more than 95% by weight, the impact resistance of the polypropylene resin molded body is deteriorated.

If the content of the α-olefin other than propylene as the monomer unit in the component (b) is out of the above range, the impact resistance of the polypropylene resin molded product is lowered.

When the intrinsic viscosity [η] of the component (b) is less than 2 dl / g, the impact resistance of the polypropylene resin molded article may decrease, and when the intrinsic viscosity [η] is more than 10 dl / g, The rigidity and heat resistance may be insufficient.

To reiterate, the composition in the present invention contains the polypropylene resin and the nucleating agent in a specific ratio.

As the nucleating agent, an organic nucleating agent and an inorganic nucleating agent can be used.

Examples of the organic nucleating agent include a metal salt of benzoic acid having an alkyl group substituted on an aromatic ring or a derivative thereof (aluminum salt of pt-butylbenzoate, etc.); dibenzylidene sorbitol and its derivative (1,3,2, 4-dibenzylidene sorbitol, 1,3,2,4-di (p-methylbenzylidene) sorbitol, 1,3,2,4-di (p-chlorobenzylidene) sorbitol, 1,3,2,4-di ( p-methoxybenzylidene) sorbitol etc.); bis (4-t) phosphate
-Butylphenyl) sodium, calcium oxalate,
Organic acid salts such as magnesium stearate, zinc salicylate and calcium tartrate can be mentioned.

Examples of the inorganic nucleating agent include talc, clay, mica, montmorillonite, clay such as bentonite, calcium silicate, magnesium silicate, calcium sulfate, barium sulfate, calcium carbonate, inorganic salts such as magnesium carbonate, Examples thereof include metal oxides such as alumina, titanium oxide, iron oxide, magnesium oxide and zinc oxide.

Among the various nucleating agents, aluminum salts such as metal salts of benzoic acid in which an alkyl group is substituted with an aromatic ring are particularly preferable as the organic nucleating agent, and talc is preferable as the inorganic nucleating agent.

The content of the nucleating agent is 0.005 to 1 part by weight, particularly 0.01 to 0.5 part by weight, based on 100 parts by weight of the polypropylene resin.

If the blending amount of this nucleating agent is less than 0.005 parts by weight, improvement in rigidity, heat resistance and hardness of the polypropylene resin molded article cannot be expected, and if the blending amount is more than 1 part by weight. However, the rigidity of the polypropylene resin molded body is not further improved.

In this composition, other additives may be contained within the range not impairing the object of the present invention.

Examples of such additives include various additives such as antistatic agents, colorants, flame retardants, antioxidants, ultraviolet absorbers, plasticizers and heat stabilizers.

Various surfactants can be used as the antistatic agent. Examples of the colorant include a sparingly soluble azo dye, a red colorant, cadmium yellow, cream yellow, and titanium white. As the flame retardant,
For example, inorganic antimony oxide, zircon oxide and the like, organic phosphates, tricresyl phosphate and the like can be mentioned. As the antioxidant, hindered phenol type, phosphorus type (phosphorous acid ester, phosphoric acid ester), sulfur type and amine type are used. Further, as the plasticizer, for example, butyric acid biester,
Examples include butanol diester and phosphoric acid diester. As the ultraviolet absorber, those such as benzotriazole type and benzophenone type are used.

In this invention, the composition is molded, and the obtained polypropylene resin molded body is heat-treated at a predetermined temperature.

The molding of the composition may be any of injection molding, film molding, blow molding, extrusion molding, compression molding and the like.

The heating temperature for heating the unoriented compact is 155 to 155.
It is preferably within a temperature range of 170 ° C. and within a temperature range of ± 4 ° C. of the melting point of the composition after the addition of the nucleating agent and before the heat treatment, and particularly within a temperature range of 158 to 168 ° C. It is also preferable that the temperature range is ± 4 ° C. of the melting point of the composition.

When the heating temperature is out of the above range, the rigidity, heat resistance and hardness of the polypropylene resin molded body cannot be expected to be significantly improved,
On the other hand, if the temperature is higher than 170 ° C., the polypropylene resin molded product will be melted, and even if the melted product is cooled, it is not possible to obtain a product with improved rigidity.

The method of heat treatment is not particularly limited as long as it is under an atmosphere that does not substantially promote the deterioration or decomposition of the polypropylene resin molded body itself or each component constituting the polypropylene resin molded body, and various methods can be adopted. it can. As the method of the heat treatment, for example, a method of heating in a mold held in the temperature range, a roll surface held in the temperature range, a method of contacting with a hot plate surface, in the temperature range, nitrogen, argon, Examples thereof include a method of arranging or immersing the polypropylene resin molding in a gas such as air or an inert liquid such as silicon oil or water. As a method of heating these, generally, an electric heater, a heat transfer oil, a sleeve, etc. are used, but the method is not limited to this, and in addition to this, a substance having a high dielectric constant such as carbon black or nitriding in the composition. Polypropylene resin molded product obtained by adding a small amount of silicon, metal oxide, an organic substance having a reactive functional group such as a carboxylic acid group, a hydroxyl group, an amino group, or an oligomer to the composition and molding the composition. It is possible to employ a method of heating the high frequency. This high-frequency heating treatment is excellent in that the heat treatment time can be significantly shortened.

A heat treatment time of 1 second or more is sufficient, but in consideration of thermal deterioration, 60 minutes is usually sufficient.

By this heat treatment, improvement in mechanical properties, temperature characteristics, hardness and the like of the polypropylene resin molded body can be achieved.

EFFECTS OF THE INVENTION According to the present invention, rigidity, heat resistance and high hardness, mechanical properties such as impact resistance, creep characteristics and fatigue characteristics, temperature characteristics such as dimensional stability at high temperatures, high A polypropylene resin molded body that is excellent in abrasion resistance because of its hardness can be manufactured by a simple operation called heat treatment.

[Examples] (Examples 1 to 7, Comparative Examples 1 to 11) A composition prepared by mixing 100 parts by weight of a propylene resin of the type shown in Table 1 and a nucleating agent having a blending weight shown in Table 1 was injected. A test piece was obtained by molding. Each test piece was prepared so as to have dimensions according to the measurement method described below.

This test piece, which is a polypropylene resin molded body, was immersed in a silicone oil bath at the temperature shown in Table 1 for the time shown in Table 1. The test piece after immersion was evaluated for various physical properties.

The description and evaluation method of the propylene resin and the core material used are shown below. The measurement results are shown in Table 1.

{Block PP-1} A propylene composition produced by two-step polymerization. That is, 84% by weight of a propylene homopolymer having an intrinsic heat [η] of 1.37 dl / g, an intrinsic viscosity [η] of 4.1 dl / g and a propylene-ethylene copolymer containing 38% by weight of ethylene as a monomer unit. And 16% by weight of polymer.

{Block PP-2} 77% by weight of a propylene homopolymer having an intrinsic viscosity [η] of 1.77 dl / g, and an intrinsic viscosity [η] of 4.7 dl / g and containing 53% by weight of ethylene as a monomer unit. And 23% by weight of the propylene random copolymer.

{Homo PP-1} Intrinsic viscosity [η] is 2.21dl / g and density is 0.89
It is a propylene homopolymer of 9 g / cm ² .

{Homo PP-2} Intrinsic viscosity [η] is 1.63dl / g and density is 0.903g /
It is a propylene homopolymer having a cm ² .

The melting point of the composition comprising the four types of polymers and the nucleating agent is
Before heat treatment, it is 163-164 ℃.

{PTBBA-Al} aluminum salt of p-t-butylbenzoate {talc} Average particle size of about 1 μm Measurement method Flexural modulus; JIS K7203 was used.

 Izod impact strength; heat distortion temperature based on JIS K7110; based on JIS K7207.

 Rockwell hardness: Based on JIS K7202.

Claims (4)

[Claims] 1. An unoriented molded article obtained by molding a composition containing a polypropylene resin and a nucleating agent mixed in a proportion of 0.005 to 1 part by weight with respect to 100 parts by weight of the polypropylene resin, A method for producing a polypropylene resin molded product, which comprises heat-treating in a temperature range of 155 to 170 ° C. and a temperature range of ± 4 ° C. of the melting point of the composition. 2. The polypropylene resin has a melting point of 16
The method for producing a polypropylene resin molded article according to claim 1, wherein the temperature is from 0 to 165 ° C. 3. The polypropylene resin has an intrinsic viscosity [η] of 1.0 to 4.0 dl / g and an isotactic pentad fraction [I] of the following formula [I] ≧ −1.02 [ The manufacturing method of the polypropylene resin molding according to claim 1 or 2, which is a propylene homopolymer satisfying η] +96.0. 4. The polypropylene resin comprises (a) an α-olefin other than propylene as a monomer unit (2).
The intrinsic viscosity [η] is 0.9-
Propylene homopolymer and / or propylene copolymer 55 to 95% by weight of 4.0 dl / g, and (b) an α-olefin other than propylene as a monomer unit in an amount of 15 to 80% by weight and an intrinsic viscosity [ Propylene copolymer 4 having an [η] of 2 to 10 dl / g
The method for producing a polypropylene resin molded article according to claim 1 or 2, which is a composition comprising 5 to 5% by weight.