JPH09143315A - Polyethylene resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyethylene resin composition which is remarkably improved in molding cycle and gives a molding remarkably improved in rigidity and transparency by blending an ethylene/α-olefin copolymer having a density in a specified range with a PP resin. SOLUTION: This composition consists of a copolymer (A) of ethylene and a 3C or higher α-olefin, of which the density when immersed in hot water at 100 deg.C for 1hr and allowed to cool in the state as it is to room temperature is 0.870-0.950g/cm<3> and a polyoropylene resin (B) at a weight ratio of copolymer A to resin B of (99.9:0.1) to (95:5). The resin B acts as the crystallization nucleator for the copolymer A, resulting in remarkable improvements in molding cycle, rigidity and transparency.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyethylene resin composition. More specifically, the present invention relates to a polyethylene resin composition capable of obtaining a molded product in which the molding cycle property during molding is remarkably improved and the rigidity and transparency are remarkably improved.

[0002]

2. Description of the Related Art Ethylene / α-olefin copolymers are
The density varies depending on the copolymer composition. A copolymer having a small amount of α-olefin has a high density and a high rigidity. Further, since the crystallization rate is high, the cycleability at the time of molding is good. However, the transparency is poor. On the other hand, when the amount of α-olefin is large, the copolymer has a low density and the transparency is good. However, since the rigidity is low and the crystallization rate is low, the cycleability at the time of molding becomes poor.

As described above, in the ethylene / α-olefin copolymer, the characteristics relating to rigidity, crystallization rate and the characteristics of transparency change with the tendency of contradictory to changes in the copolymer composition, that is, density. Therefore, a single copolymer cannot have both properties.

However, recently, these ethylene / α
-Olefin copolymers are also required to have higher performance in the market as their fields of use are expanded. In particular, there are many demands for the properties of a high-density copolymer, that is, high rigidity and high crystallization rate, and the properties of a low-density copolymer, that is, high transparency.

In order to meet these requirements, a general method is to blend with different resins or, in the case of a crystalline resin such as an ethylene / α-olefin copolymer, add a crystal nucleating agent. It is mentioned as a thing. Of these, the former blending with different resins is often due to an additive effect.

That is, in order to achieve high rigidity, a method of blending a resin having high rigidity corresponds to this.
Even in ethylene / α-olefin copolymers, relatively many polypropylene-based resins and high-density polyethylene (H
DPE) may be blended to increase the rigidity. However, this method can improve the characteristics of interest,
It is difficult to give several characteristics at the same time. further,
If the amount is extremely small, the effect of increasing the rigidity is small, so a certain amount must be added, and other properties may deteriorate.

On the other hand, the latter method of adding a crystal nucleating agent is a method of forming more crystals within a certain time during the cooling process. Therefore, by adding the crystal nucleating agent, the crystallization rate is increased and the amount of crystals is increased, so that the rigidity is also improved. Further, since the size of each crystal aggregate is reduced, the amount of visible light scattered is reduced and the transparency is improved. Thus, the method using a crystal nucleating agent can simultaneously improve the crystallization rate, rigidity and transparency. Therefore, in the ethylene / α-olefin copolymer, it is possible to improve the transparency of the high-density copolymer and further improve the rigidity and the crystallization rate, which are the original characteristics. it can. Further, for a low-density copolymer, it is possible to further improve the transparency, which is the original feature, while improving the rigidity and the crystallization rate. Further, in the case of a crystal nucleating agent, the addition amount thereof is generally a very small amount of 2% by weight or less, and there is almost no adverse effect on other characteristics.

From the above, in order to meet the high demands of the market, many substances of ethylene / α-olefin copolymers have been evaluated for their potential as nucleating agents. However, it is known that an ethylene-based polymer containing an ethylene / α-olefin copolymer has some effect on metal salts of benzoic acid, talc and the like, but it is not sufficient. Not all of them show great effects, but if they are not molded at a high temperature, the effects are not exhibited and there is a risk of deterioration or coloring depending on the resin.
Therefore, in order to produce ethylene / α-olefin copolymers that meet the high demands of the market, we have discovered a crystal nucleating agent that exerts a great effect in the temperature range where the thermal stability of the copolymer is maintained. The main point is to do.

Recently, metallocene catalysts have made it possible to obtain ethylene / .alpha.-olefin copolymers having a small amount of low molecular weight components and a uniform composition distribution as compared with conventional copolymers. It was Based on their molecular structures, these novel copolymers are highly transparent, have high impact resistance, and are less sticky than conventional copolymers, and are attracting attention as new materials.
However, since the copolymer has a uniform composition distribution, the crystallization rate in the cooling process is slow, and the molding cycle property is slower than that of the conventional copolymer.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyethylene resin composition capable of obtaining a molded product which is remarkably improved in molding cycle property and rigidity and transparency.

[0011]

The inventor of the present invention has made extensive studies to solve the above-mentioned problems, and as a result, completed the present invention. That is, the present inventor found that the polypropylene resin acts as a crystal nucleating agent for an ethylene / α-olefin copolymer in a specific density range, and as a result, the ethylene / α-olefin copolymer was found. It has been found that a composition comprising a polypropylene resin and a polypropylene resin has remarkably improved molding cycle property, rigidity and transparency. The present invention is characterized by the fact that a polypropylene-based compound acts as a crystal nucleating agent for ethylene / α-olefin copolymers, which is novel.

That is, according to the present invention, 1
A copolymer [A] of ethylene and an α-olefin having a carbon number of 3 or more [A] having a density in the range of 0.870 to 0.950 g / cm ³ after being soaked in time and allowed to cool to room temperature in that state, and a polypropylene type Consisting of resin [B],
[A]: [B] is 99.9: 0.1-95 by weight fraction:
The polyethylene resin composition is characterized in that it is in the range of 5, preferably in the range of 99.5: 0.5 to 97: 3.

The present invention will be described in detail below.

The α-olefin in the ethylene / α-olefin copolymer of the above [A] is, for example, propylene, butene-1, pentene-1,1-methylbutene-1, hexene-1,4-methylpentene-. 1, octene-1, nonene-1, decene-1, undecene-1, dodecene-1, tridecene-1, tetradecene-1, pentadecene-1, hexadecene-1, heptadecene-1,
Octadecene-1, nonadecene-1, eicosene-1, etc. are mentioned, and these 1 type (s) or 2 or more types are used. Among them, butene-1 and penten-
1, hexene-1, 4-methylpentene-1, octene-1 and the like are preferable.

Further, the ethylene / α-olefin copolymer of [A] was soaked in hot water at 100 ° C. for 1 hour and allowed to cool to room temperature, and the density was 0.870-.
It is in the range of 0.950 g / cm ³ . The present invention provides [B]
The polypropylene-based resin (1) acts as a crystal nucleating agent for the ethylene / α-olefin copolymer (A).
The crystal nucleating agent serves as a seed (starting point) of crystals in crystallization, and it is meaningless to add the crystal nucleating agent unless the resin is crystalline and can crystallize in a molecular structure.
When the density of the ethylene / α-olefin copolymer [A] is less than 0.870 g / cm ³ , the amount of α-olefin is large and the crystallinity is almost lost. Therefore, it is meaningless to add the polypropylene resin [B] to such a copolymer. Moreover, the density is 0.950 g /
The effect of adding the polypropylene resin of [B] is not sufficient for the ethylene / α-olefin copolymer [A] exceeding cm ³ .

The molecular weight distribution (Mw / Mn) of the ethylene / α-olefin copolymer [A] in the present invention is not particularly limited, but is preferably 3 or less. When the molecular weight distribution is 3 or more, the stickiness of the surface of the molded product due to the low molecular weight component may be a problem.

The method for producing the ethylene / α-olefin copolymer [A] in the present invention is not particularly limited, and it can be produced using various catalysts such as titanium-based catalysts, vanadium-based catalysts or metallocene-based catalysts. it can. Among them, it is preferable to use a metallocene-based catalyst that is easy to obtain an ethylene / α-olefin copolymer that satisfies the above-mentioned conditions regarding the molecular weight distribution.

That is, a catalyst comprising (a) a transition metal compound containing a transition metal of Group 4 of the periodic table, (b) a compound which reacts with the transition metal compound to form an ionic complex, and / or (c) an organometallic compound. The ethylene / α-olefin copolymer can be produced by copolymerizing ethylene and the α-olefin in the presence of

Polymerization can be carried out by any of batch method, semi-continuous method and continuous method, and it is also possible to carry out in two or more stages by changing the polymerization conditions. The copolymer obtained after the completion of the polymerization is separated and recovered from the polymerization solution by a conventionally known method, and dried to obtain a solid copolymer.

The polypropylene resin [B] in the present invention may be a commonly used polypropylene resin. For example, propylene homopolymer, propylene having an ethylene content of 0.5 to 12% by weight.
Ethylene random copolymer, ethylene content 0.5-1
2% by weight, 1-butene-like α-olefin content of 0.5 to 20% by weight polypropylene / ethylene / α-
Examples include olefinic terpolymers and crystalline polypropylene resins that are impact polypropylene having an ethylene content of 1 to 60% by weight, and one or more of them are used. Among them, propylene homopolymer is preferable, and further, differential scanning calorimeter (DSC)
At 200 ° C. for 5 minutes, the peak temperature (Tc (PP)) of the crystallization exothermic peak located at the highest temperature when cooled at a constant rate of 10 ° C./min is 125 ° C.
The above is desirable. Even if Tc (PP) is lower than 125 ° C., the effect is sufficiently obtained, but in this case, the effect becomes small when the melting temperature of the resin at the time of molding is high. This is particularly noticeable when static heat is applied without adding kneading in the melting stage during molding such as compression molding. With Tc (PP) of 125 ° C. or higher, there is no such problem, and the effect is stably exhibited by any molding method and conditions. The polypropylene resin having a Tc (PP) of 125 ° C. or higher can be obtained by, for example, improving the isotactic stereoregularity.
Further, a polypropylene-based resin composition can be obtained by adding a known crystal nucleating agent typified by a metal salt of benzoic acid to a crystalline polypropylene-based resin.

These polypropylene-based resins can be obtained by a conventionally known method using a Ziegler-based catalyst, and can also be obtained by using a metallocene catalyst.

The modifying effect of the composition of the present invention and the improvement of crystallization rate, rigidity and transparency of the ethylene / α-olefin copolymer is the same as that of the ethylene / α-olefin copolymer of [A] [B]. The polypropylene resin of [A]:
[B] The weight fraction is in the range of 99.9: 0.1 to 95: 5,
Preferably, it can be obtained by mixing in a range of 99.5: 0.5 to 97: 3. [B]
Is less than 0.1% by weight, the effect of [A] as a crystal nucleating agent on the ethylene / α-olefin copolymer is not sufficient, and when it exceeds 5% by weight, ethylene / α -Although it has an effect as a crystal nucleating agent for an olefin copolymer, it is not preferable because the amount of the propylene resin [B] is too large and the presence itself causes deterioration of transparency. In particular, when added to a low-density ethylene / α-olefin copolymer having relatively good transparency, the effect is great.

In the polyethylene resin composition of the present invention, various phenol-based, phosphite-based, thioether-based antioxidants, fatty acid metal salts, hydroxy fatty acid metal salts, and alkyl lactic acid metals may be added, if desired. Neutralizers such as salts and hydrotalcite, UV absorbers such as benzophenone, benzotriazole, salicylate, hindered amine light stabilizers, lubricants, antiblocking agents, antistatic agents, metal salts of organic acids and dispersants. , Pigments and the like can be added.

The composition of the present invention can be produced by any method, but for ease of handling and improvement of dispersibility, rolls, plastomills, uniaxial and biaxial.
It is preferable to use a suitable kneading machine such as a shaft extruder, a kneader or a Banbury mixer to heat and knead at a melting point of both resins or higher.

The polyethylene resin composition thus obtained is a resin molding material which is applied to known molding methods such as injection molding, extrusion molding, compression molding, blow molding, injection blow molding, inflation molding and cast molding. Used as. In addition, the composition of the present invention can also obtain the target molded product by a method of preparing a highly filled resin in advance and adding these at the time of molding or re-kneading, that is, by adding in a masterbatch.

[0026]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

The characteristics of the resins used in Examples and Comparative Examples are measured by the following methods.

Density of Ethylene / α-Olefin Copolymer According to JIS K6760, the density of a product obtained by immersing in hot water at 100 ° C. for 1 hour and allowing it to cool to room temperature at 23 ° C. It was measured with a tube.

M of ethylene / α-olefin copolymer
w / Mn Ratio (Mw / Mn) of weight average molecular weight (Mw) and number average molecular weight (Mn) of ethylene / α-olefin copolymer
Is Waters Co., Ltd. 150 CALC / GPC
(Column: Tosoh Corporation, GMHHR-H (S),
7.8 mm IDX 30 cm x 3, solvent 1,2,4-trichlorobenzene, temperature 140 ° C, flow rate: 1.0 ml /
Min, injection temperature: 30 mg / 30 ml (injection amount 300 μ
Mw and Mn were measured by the gel permeation chromatography method using 1)), and Mw / Mn was calculated. The column elution volume was calibrated by the universal calibration method using standard polystyrene manufactured by Tosoh Corporation.

Crystallization temperature of polypropylene resin (T
c (PP)) Differential scanning calorimeter (Perkin Elmer Co., Ltd., DSC
-7), after holding at 200 ° C. for 5 minutes, 10
The peak temperature of the crystallization exothermic peak located at the highest temperature obtained when cooled at a constant rate of ℃ / min is the crystallization temperature (T
c (PP)).

Melt Flow Rate (MFR) According to JIS K7210, it was measured under the load of 2160 g at 190 ° C. for ethylene / α-olefin copolymer and 230 ° C. for polypropylene resin.

Two kneading methods were used to prepare the compositions in the examples and comparative examples. This is to confirm that there is no extreme difference in effect depending on the kneading method. One is using a Brabender mixer (hereinafter,
Abbreviated as a mixer method), an ethylene / α-olefin copolymer and a polypropylene resin are mixed, and 2,6-di-t-butyl-4-hydroxytoluene (1000 ppm) is added as an antioxidant to Toyo Seiki Co., Ltd. 2) was used for melt kneading at 180 ° C. for 10 minutes at a rotation speed of 50 rpm. The other is a method using a single screw extruder (hereinafter, abbreviated as single screw extrusion method).
Then, the resin and the antioxidant were mixed in the same manner as in the mixer method, and the mixture was extrusion kneaded at a cylinder temperature of 200 ° C. and a rotation speed of 50 rpm. The single screw extruder is manufactured by Placo Co., Ltd.

Here, the molding cycle, rigidity and transparency were evaluated. Molding cycle property was evaluated by using differential scanning calorimeter (DSC) to evaluate the peak temperature (Tc) of the crystallization exothermic peak of the ethylene / α-olefin copolymer component obtained when cooled from a molten state at a constant rate. did. T
The higher c is, the faster the crystallization rate under the same cooling condition is, which corresponds to the better molding cycle property. The rigidity was evaluated by Young's modulus, and the transparency was evaluated by haze.

Haze: Haze was measured with a press sheet having a thickness of 200 μm obtained by compression molding. The compression molding machine was manufactured by Kansai Roll Co., Ltd., and two of them were used. One is for melting the kneaded product (melting side), and the other is for cooling (cooling side). Specifically, it is 15 on the melting side.
Hold at 0 ° C for 12 minutes, then quickly move to the 30 ° C cooling side. Further, regarding the effect of melting at a high temperature, the temperature of the compression molding machine on the melting side was 170 ° C., and the same was applied thereafter. The haze of the obtained press sheet was measured according to JIS K71 using a haze meter manufactured by Nippon Denshoku Industries Co., Ltd.
It measured based on 05.

Young's modulus: A dumbbell test piece (effective sample length 10 mm, width 3.2 mm) was punched out from the above press sheet to obtain a measurement sample. For the measurement, a tensile tester manufactured by Orientec Co., Ltd. was used, and the chuck distance was 28 m.
m, and the pulling speed was 20 mm / min. Young's modulus was estimated from the gradient of the initial linear region of the stress-strain curve obtained at that time.

Crystallization temperature (Tc): The crystallization temperature is a differential scanning calorimeter (manufactured by Perkin Elmer Co., Ltd., DSC-
It measured using 7). About 5 mg from the above press sheet
Was sampled, and in a differential scanning calorimeter,
It was kept at 0 ° C. for 5 minutes and then cooled at a constant rate of 10 ° C./minute. The peak temperature of the crystallization exothermic peak of the ethylene / α-olefin copolymer component obtained at that time was defined as the crystallization temperature (Tc).

The present invention will be described in more detail with reference to specific examples and comparative examples. Tables 1 and 2 show the ethylene / α-olefin copolymer [A] and polypropylene used in the examples and comparative examples, respectively. A list of system resins [B] is shown.
[B5] was used for the example of claim 2, and 1500 ppm of aluminum benzoate was added to homopolypropylene. Crystallization temperature (Tc (PP))
Is 131.1 ° C.

[0038]

[Table 1]

[0039]

[Table 2]

Example 1 and Comparative Example 1 Example 1 is a composition comprising 99% by weight of ethylene and a hexene-1 copolymer [A1] obtained using a Ziegler catalyst and 1% by weight of homopolypropylene [B1]. Is.
The characteristics of [A1] and [B1] are shown in Tables 1 and 2, respectively. Comparative Example 1 is a single item [A1]. The kneading is a mixer method. Table 3 shows the haze, Young's modulus, and crystallization temperature of Example 1 and Comparative Example 1.

[0041]

[Table 3]

Examples 2 to 5 and Comparative Example 2 In Examples 2 to 5, 99% by weight of ethylene / hexene-1 copolymer [A2] obtained by using a metallocene catalyst and 4 types of homopolypropylene having different molecular weights are used. 1% by weight of the composition. The four types of polypropylene are [B1], [B2], [B3], and [B4], respectively.
The characteristics of [A2] are shown in Table 1, and the characteristics of [B1] to [B4] are shown in Table 2. [B4] is a commercially available polypropylene wax. Comparative Example 2 is a single item [A2]. The kneading is a mixer method. For the polymerization of [A2], diphenylmethylene (cyclopentadienyl) as a metallocene compound is used.
(Fluorenyl) zirconium dichloride, N, N-dimethylanilinium tetrakis (pentafluorophenyl) borate as an ionic compound, and triisobutylaluminum as an organic aluminum compound were used.
The metallocene compound, ionic compound and organoaluminum compound were used in a molar ratio of 1: 2: 250, and toluene was used for the preparation of the catalyst. [A2] uses the above catalyst system and has a polymerization temperature of 165 ° C. and a polymerization pressure of 900 kgf / cm.
It was obtained by polymerizing in ² . Table 4 shows the haze, Young's modulus and crystallization temperature of Examples 2-5 and Comparative Example 2.

[0043]

[Table 4]

Example 6, Comparative Examples 3 to 5 Example 6 confirms the influence of the kneading method when kneading the composition. Here, kneading was performed by a single screw extrusion method. Example 6 is an ethylene obtained by using a metallocene catalyst.
A composition comprising 99% by weight of a hexene-1 copolymer [A3] and 1% by weight of a commercially available polypropylene wax [B4]. [A3] was obtained under the same catalyst system and polymerization conditions as [A2]. The features of [A3] and [B4] are
They are shown in Tables 1 and 2, respectively. Comparative Example 3 is a single product of [A3], Comparative Example 4 is a composition in which 2000 ppm of talc is added to [A3], and Comparative Example 5 is [A3] containing 2 parts of aluminum benzoate.
This is a composition added with 000 ppm. Table 5 shows the haze, Young's modulus and crystallization temperature of Example 6 and Comparative Examples 3-5.

[0045]

[Table 5]

Example 7, Comparative Example 6 In Example 7, [A2]: [B1] is 99: 1 in weight fraction.
It has been confirmed that the effect of the composition can be exhibited even when the cooling rate at the time of producing a molded product is changed. Here, the heater was turned off and allowed to cool to room temperature without moving from the state of holding the temperature at 150 ° C. by the compression molding machine on the melting side to the compression molding machine on the cooling side at 30 ° C. to produce a press sheet. Here, the haze was evaluated. [A2],
The characteristics of [B1] are shown in Tables 1 and 2, respectively. Comparative Example 6
Is an evaluation of the single [A2] under the same conditions. Table 6 shows the haze of Example 7 and Comparative Example 6.

[0047]

[Table 6]

Example 8 and Comparative Examples 7 and 8 Example 8 is an example corresponding to claim 2 and comprises 99% by weight of an ethylene / hexene-1 copolymer [A2] and a propylene resin composition [B5] 1. It is a composition consisting of 10% by weight. The characteristics of [A2] and [B5] are shown in Tables 1 and 2, respectively. Comparative Example 7 is a composition of [A2] alone, and Comparative Example 8 is the same composition as in Example 2 consisting of 99% by weight of [A2] and 1% by weight of [B5]. In Example 8 and Comparative Examples 7 and 8 described here, when the press sheet was prepared and the crystallization temperature (Tc) of the ethylene / α-olefin copolymer component was measured using a differential scanning calorimeter (DSC). The melting temperature of is 170 ° C. Table 7 shows haze, Young's modulus and crystallization temperature of Example 8 and Comparative Examples 7 and 8.

[0049]

[Table 7]

[0050]

Industrial Applicability As described above, the polyethylene resin composition of the present invention can improve the molding cycle property based on the increase of the crystallization temperature, that is, the crystallization speed, and can significantly improve the rigidity and the transparency. In addition, the effect is stably exhibited under all cooling conditions.

Therefore, it is possible to improve the production efficiency of the product, and its use is in fields requiring high rigidity and / or high transparency, such as injection molded products such as caps and garment cases, and bottles. A composition suitable for producing blow products represented by, injection blow products represented by various containers, extrusion molded products represented by pipes, and stretched or non-stretched film molded products represented by packaging films. is there.

[0052]

Claims (2)

[Claims] 1. Density of 0.870-0.40 after being soaked in hot water of 100 ° C. for 1 hour and allowed to cool to room temperature as it is.
Copolymer of ethylene and α-olefin having 3 or more carbon atoms in the range of 950 g / cm ³ (hereinafter referred to as [A])
And a polypropylene-based resin (hereinafter referred to as [B]), and [A]: [B] are 99.9: 0.1 by weight fraction.
The polyethylene resin composition is in the range of 95: 5. 2. The polypropylene resin according to claim 1 is most obtained when held in a differential scanning calorimeter (DSC) at 200 ° C. for 5 minutes and then cooled at a constant rate of 10 ° C./minute. A polyethylene resin composition having a peak temperature (Tc (PP)) of a crystallization exothermic peak located at a high temperature of 125 ° C. or higher.