JPH056576B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a polypropylene composition comprising polypropylene, an ethylene/α-olefin copolymer, and a specific block copolymer. More specifically, the present invention relates to a polypropylene composition suitable for use as an inner stopper of a polypropylene container, which has excellent heat resistance and transparency, has heat-sealability with polypropylene, and is easy to tear into pieces. [Conventional technology] Polypropylene has good hygiene, heat resistance, transparency,
It has excellent gloss and surface hardness, and is used in a variety of applications including films, containers, and containers.
Among these, blow-molded containers, especially biaxially stretched blow-molded containers, have further improved properties and excellent impact resistance, and are therefore particularly suitable for containers for liquid seasonings such as soy sauce and sauces, containers for pharmaceuticals, and the like. The inner stopper of such a container is usually made of polyethylene or polypropylene and is screwed or fitted.
When used, it is removed or parts are torn off. However, depending on the use of the container, it is necessary to heat-treat the inner stopper after heat-sealing it to the container, and in that case, it is necessary to make the inner stopper heat-sealable to the container and to take out the contents. Ease of tearing is also required. However, at present, there is no composition suitable for use as an inner stopper for polypropylene containers. In other words, polypropylene inner plugs have excellent heat-sealability, but are extremely difficult to tear into strips, while polyethylene inner plugs are easy to tear into strips, but
It does not heat-seal with polypropylene at all. Furthermore, even if polypropylene and polyethylene are mixed, it is difficult to obtain a material with an excellent balance between heat-sealing properties and ease of tearing into pieces. On the other hand, a composition obtained by mixing a polyolefin with a block copolymer obtained by hydrogenating the polybutadiene portion of a polystyrene-polybutadiene-polystyrene block copolymer suppresses whitening of the polyolefin when folded (Japanese Patent Publication No. 41-2909, Kimiaki
55-18739), or that it has excellent heat resistance and transparency (Japanese Patent Application Laid-Open No. 58-215446). However, even if the compositions described in these publications, in which polypropylene alone, polyethylene alone, or a hydrogenated block copolymer added to polyethylene alone, are used as the inner stopper of a polypropylene container, the same thermal melting effect as described above is obtained. It is not possible to obtain a product with an excellent balance between adhesion and ease of tearing. Furthermore, a composition in which linear low-density polyethylene and a thermoplastic elastomer are added to crystalline polypropylene is also known (Japanese Unexamined Patent Publication No. 101135/1982), Even if a composition containing a thermoplastic elastomer such as a polymer or an ethylene-propylene-diene copolymer is used, the ease of tearing into pieces is not improved at all, and neither can be used as a material for the inner stopper of polypropylene containers. That was the current situation. [Problems to be Solved by the Invention] In view of this situation, the present inventors have developed a sealing material for polypropylene containers that is heat resistant and has a good balance between fusion properties with polypropylene and ease of tearing into pieces. As a result of various studies to develop materials particularly suitable for the inner plug, it was found that a polypropylene composition consisting of polypropylene, a specific ethylene/α-olefin copolymer, and a specific block copolymer has the above characteristics. I understand this and have completed the present invention. [Means for solving the problems] That is, the present invention provides polypropylene (A): 20 to 90 parts by weight, density:
0.890 to 0.940g/cm ³ , crystallinity by X-ray:
Copolymer (C) of ethylene and α-olefin having 4 to 20 carbon atoms and 10 to 64% and melting point: 110 to 127°C: 80 to 10 parts by weight, and polypropylene (A) + ethylene/α-olefin copolymer Based on 100 parts by weight of polymer (C), the monovinyl-terminated aromatic hydrocarbon polymer block S constitutes 8 to 55% by weight of the block copolymer (D), and at least two monovinyl-terminated aromatic hydrocarbon polymers Consisting of a heavy hydrocarbon block S and at least one intermediate conjugated diolefin polymer block B, and 25% or less of the aromatic double bonds of the polymer block S and at least 25% of the aliphatic double bonds of the conjugated diolefin polymer block B. Partially hydrogenated block copolymer (D) in which 80% is reduced by hydrogenation: 1 or
100 parts by weight of the polypropylene composition, which has heat resistance and ease of tearing into pieces, and has heat fusion properties with polypropylene. [Function] The polypropylene (A) used in the present invention is a homopolymer of propylene or propylene and 40 mol% or less of other α-olefins, such as ethylene, 1-
It is a crystalline random or block copolymer with butene, 1-hexene, 4-methyl-1-pentene, 1-octene, etc. Among these, a propylene homopolymer, preferably a propylene homopolymer having an isotactic index of 90 or more, more preferably 95 or more, and an ethylene content of 5 to 40 mol%, preferably 10 to 35 mol% A propylene/ethylene block copolymer is preferred. Polypropylene (A) usually has a melt flow rate (MFR(L); ASTM D 1238, L) of 1 to 100 g/10 min, preferably 10 to 50.
g/10min range. MFR(L) is 1
If it is less than 100 g/10 min, there is a risk that the ease of tearing into pieces will be impaired, while if it exceeds 100 g/10 min, the mechanical strength will tend to be low. The ethylene content of polypropylene (A) is ¹³ C−
This is a value measured by NMR method, and the isotactic index () is expressed as a percentage by weight of boiling n-heptane insoluble matter. The ethylene/α-olefin copolymer (C) used in the present invention has a density (ASTM D 1505): 0.890 to
0.940g/cm ³ , preferably 0.910 to 0.930g/
cm ³ , X-ray crystallinity: 10 to 64%, preferably 45 to 57% and a melting point of 110 to 127°C, preferably 115 to 125°C, and ethylene with a carbon number of 4 to 20, preferably 5 to 18 - It is a copolymer with olefin. If the density is less than 0.890 g/cm ³ and the crystallinity is less than 10%, the heat resistance will decrease. On the other hand, those with a crystallinity of more than 0.940 g/cm ³ and 64% are difficult to tear and cannot achieve the purpose of the present invention. Also, those with a melting point of less than 110°C will have poor heat resistance, and those with a melting point of over 127°C will be difficult to tear into pieces. Ethylene/α-olefin copolymer (C) usually has a melt flow rate (MFR(E): ASTM D
1238, E) is 1 to 50g/10min, preferably
It is in the range of 10 to 30g/10min. Those with MFR(E) of less than 1 g/10 min tend to have poor moldability, while those with MFR(E) of more than 50 g/10 min tend to have poor mechanical strength. The melting point of the ethylene/α-olefin copolymer (C) is one or more, often two or more, determined from the endothermic curve of a differential scanning calorimeter (DSC) at a heating rate of 10°C/min This is the highest temperature among the three endothermic peaks. In the ethylene/α-olefin copolymer (C), examples of α-olefins having 4 to 20 carbon atoms copolymerized with ethylene include 1-butene, 1-
Mention may be made of pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-tetradecene, 1-octadecene, or a mixture of at least two thereof. The ethylene/α-olefin copolymer (C) of the present invention having the above properties is produced by using a transition metal catalyst, such as a highly active titanium catalyst formed from a magnesium compound and a titanium compound, by a so-called medium-low pressure method. It can be obtained by polymerizing α-olefin in a proportion that provides the required density. In order to obtain the desired melt flow rate, a molecular weight regulator such as hydrogen may be used. Polymerization can be carried out by various methods such as slurry polymerization, gas phase polymerization, and high temperature solution polymerization. The partially hydrogenated block copolymer (D) of the present invention is a monovinyl-terminated aromatic hydrocarbon polymer block S.
constitutes 8 to 55% by weight, preferably 10 to 30% by weight of the block copolymer (D), and at least 2
preferably an average molecular weight of 5,000 to 125,000,
More preferably, a terminal monovinyl-substituted aromatic hydrocarbon polymer block S having a molecular weight of 10,000 to 50,000, and at least one, preferably an average molecular weight of 10,000 to 300,000, more preferably 30,000 to 150,000.
consisting of an intermediate conjugated diolefin polymer block B and 25% of the aromatic double bonds of the polymer block S.
Preferably 5% or less and at least 5% of the aliphatic double bonds of the conjugated diolefin polymer block B.
It is a block copolymer which is 80%, preferably 99% reduced by hydrogenation. The partially hydrogenated block copolymer (D) of the present invention is linear,
It may be either radial or branched.
Methods for making such polymers are well known in the art. The structure of the block copolymer (D) is determined by the polymerization method. For example, linear polymers can be prepared by subsequent introduction of the desired monomers into the reaction vessel when using an initiator such as lithium-alkyl or dilithiostilbene, or for three or more precursor polymers. produced by coupling agents with functional groups. Coupling takes place with polyfunctional coupling agents such as dihaloalkanes or alkenes, as well as certain polar compounds such as silicon halides, siloxanes or esters of monohydric alcohols and carboxylic acids. The presence of coupling residues in the polymer is negligible for suitable types of polymers forming part of the compositions of this invention. Similarly, in a general sense, specific structures may also be ignored. The invention applies in particular to the use of selectively hydrogenated polymers with the following typical types of sequences before hydrogenation: Polystyrene-polybutadiene-polystyrene (SBS) Polystyrene-polyisoprene-polystyrene (SIS) Poly(α-methylstyrene)-polybutadiene-poly(α-methylstyrene) and poly(α-
methylstyrene)-polyisoprene-poly(α-
(methylstyrene) Both polymer blocks S and B are monopolymers insofar as each block is based on at least one monomer characterizing it and insofar as the blocks S are individually based on monovinyl-substituted aromatic hydrocarbons. Alternatively, it may be a random copolymer. The monovinyl-substituted aromatic hydrocarbon is α
- includes methylstyrene and ring-substituted styrenes, especially styrene and analogs and congeners, including ring-methylated styrenes. Preferred monovinyl-substituted aromatic hydrocarbons are styrene and alpha-methylstyrene, with styrene being particularly preferred. Block B may consist of a homopolymer of butadiene or isoprene and a copolymer of one of these two conjugated diolefins with a monovinyl-substituted aromatic hydrocarbon, so long as conjugated diolefin units predominate. When the monomer used is butadiene,
Preferably, 35 to 55 mole percent of the condensed butadiene units in the butadiene polymer block have a 1,2-configuration. Therefore, when such a block is hydrogenated, the resulting products are ethylene and butene.
1 regular copolymer block (EB) or similar. If the conjugated diene used is isoprene, the resulting hydrogenation product is a regular copolymer block of ethylene and propylene (EP) or the like. Hydrogenation of the precursor block copolymer substantially completely hydrogenates at least 80% of the aliphatic double bonds;
On the other hand, it is carried out by using a catalyst consisting of a reaction product of an aluminum alkyl compound and a nickel or cobalt carboxylate or alkoxide under conditions such that about 25% or less of the aromatic double bonds are hydrogenated. preferable. Preferred block copolymers have at least 99% aliphatic double bonds.
is hydrogenated, while 5% or less of the aromatic double bonds are hydrogenated. In the partially hydrogenated block copolymer (D) used in the polypropylene composition of the present invention, at least 80% of the aliphatic double bonds of the conjugated diolefin polymer block S must be hydrogenated as described above. The so-called SBS block copolymer described above, in which the portion is not hydrogenated, has poor heat resistance and compatibility with polypropylene (A), etc., and therefore does not meet the purpose of the present invention. This partially hydrogenated block copolymer (D) is manufactured by Shell Co. (USA).
It is manufactured and sold as Clayton G. The polypropylene composition of the present invention includes the polypropylene (A): 20 to 90 parts by weight, preferably 30 to 60 parts by weight, and the ethylene/α-olefin copolymer (C): 80 to 10 parts by weight, preferably 70 to 60 parts by weight.
40 parts by weight and polypropylene (A) + ethylene α-
The partially hydrogenated block copolymer (D) is comprised of 1 to 100 parts by weight, preferably 5 to 70 parts by weight, per 100 parts by weight of the olefin copolymer (C). The amount of ethylene/α-olefin copolymer (C) is 10
If it is less than part by weight, the tearing property will not be improved;
If it exceeds 80 parts by weight, the heat fusion properties with polypropylene will be poor. If the amount of the partially hydrogenated block copolymer (D) is less than 1 part by weight, tearability will not be improved, while if it exceeds 100 parts by weight, it will be difficult to tear (too soft). The polypropylene composition of the present invention contains additives that are usually added to thermoplastic resins, such as heat stabilizers, weather stabilizers, antistatic agents, lubricants, slip agents, nucleating agents, and plasticizers such as dyes and hydrocarbon oils. Agents may be added to the extent that the purpose of the present invention is not impaired. In order to obtain the polypropylene composition of the present invention, the polypropylene (A), the ethylene/α-olefin copolymer (C) and the partially hydrogenated block copolymer (D) are mixed in the above ranges, for example, using a Henschel mixer, V- After mixing with a blender, ribbon blender, tumbler blender, etc., use a single screw extruder, twin screw extruder, kneader, etc.
A method of melt-kneading and granulating or pulverizing the mixture using a Banbury mixer or the like can be adopted. [Effects of the Invention] The polypropylene composition of the present invention differs from conventional compositions in which a partially hydrogenated block copolymer is added to polypropylene or polyethylene. Since it has excellent heat resistance, it is suitable as a sealing material for polypropylene containers, particularly biaxially oriented polypropylene containers that have excellent heat resistance and transparency. [Examples] Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples as long as the gist thereof is not exceeded. Control example 1 MFR(L): 55g/10min, total ethylene content:
Polypropylene block copolymer with 17 mol%, propylene/ethylene rubber content (ethylene content: 40 mol%, decalin solvent intrinsic viscosity [η] at 135°C: 2.2 dl/g): 21% by weight, polyethylene content: 2% by weight. Combined (hereinafter abbreviated as PPB-) and MFR(E):
18g/10min, density: 0.920g/10min, 4-methyl-1-pentene content: 3.2 mol%, crystallinity by X-ray: 51%, melting point: 121.8℃ (other than 116.6℃
Ethylene 4-
Methyl-1-pentene copolymer (hereinafter referred to as EMP-
) in the proportions shown in Table 1 using a Henschel mixer, and then using a 40 mmφ extruder (molding temperature:
Samples 1 to 5 were obtained by melt-kneading and granulation at 200°C.
Next, using such samples 1 to 5, a 5-ounce injection molding machine (molding temperature: 200°C) was used to mold the samples to a diameter of 30 mmφ.
Thickness on the circumference of 15mmφ diameter on a 1.5mm thick disk
A pull-off type cap having a thin film portion with a thickness of 0.25 mm and a ring with a diameter of 15 mmφ attached to one place on the circumference via a pillar with a diameter of 2.5 mmφ was molded. The performance of the obtained cap was evaluated by the following method. Pulling force (Kg): 200mm/ using a tensile tester
A tensile test was conducted at a tensile speed of min, and the stress (Kg) required to break the thin film portion was defined as the tearing force. Fusion strength (Kg): Cap is heated to 200℃ for 9 seconds.
It was fused to a polypropylene sheet at a pressure of 5 Kg/cm ² (fused area 1.2 cm ² ), and after cooling, a peel test was conducted at a peeling rate of 200 mm/min, and the stress (Kg) required for peeling was taken as the fusion strength. The results are shown in Table 1. In Table 1, if the shredding force is 7 kg or more, it is impossible to use it in actual use, that is, to shred it with your fingers.
If it weighs more than 6 kg, it can be torn into pieces, but it will hurt your fingers and is not suitable for actual use. Furthermore, if the welding strength is less than 40 kg, there is a risk of liquid leaking from the welded portion during transportation, which may pose a practical problem. As a result, PPB− and EMP
It can be seen that in combination with -, a well-balanced tearing force and fusion strength cannot be obtained at any blending ratio. Example 1 Partially hydrogenated polystyrene-polybutadiene-polystyrene block copolymer with PPB-, EMP- and polystyrene content: 29% by weight used in Control Example 1 (trade name: Kraton G1652, manufactured by Siel Corporation: hereinafter referred to as SEBS-) Samples 6 to 11 were obtained in the same manner as in Control Example 1 after mixing with a Henschel mixer in the proportions shown in Table 2. Next, a cap was molded by the method described in Comparative Example 1, and its performance was evaluated. The results are shown in Table 2. As a result, it can be seen that Samples 7 to 10 have compositions with a good balance between tearing force and fusion strength. Comparative Example 1 Instead of SEBS- used in Example 1,
MFR(L): 2.9g/10min, ethylene content: 81 mol%, melting point: 48℃, crystallinity by
(abbreviated as EPR-) or MFR(L): 0.4g/10min,
Propylene-ethylene random copolymer (hereinafter abbreviated as PER-) with ethylene content: 40 mol% (X-ray crystallinity 3%) was used to blend each in the proportions shown in Table 2 (Samples 12 and 13). ) except for Example 1.The results are shown in Table 2.As a result, instead of SEBS-, EPR- or
The one using PER- has a high fusion strength, but
It can be seen that the tearing force is too large and is not suitable for actual use. Comparative Example 2 Instead of EMP- used in Example 1, MFR
(E): 0.8g/10min, density 0.954g/10min, X-ray crystallinity: 70%, melting point: 131℃ high-density polyethylene (hereinafter abbreviated as HDPE-), or MFR
(E): 6.5g/10min, density: 0.917g/10min, X
Using high-pressure low density polyethylene (hereinafter abbreviated as HPPE-) with linear crystallinity: 48% and melting point: 106°C, each was blended in the proportions shown in Table 3 (Sample 14
and 15) were carried out in the same manner as in Example 1. The results are shown in Table 3. As a result, instead of EMP−,
Those using HDPE- or HPPE-
It can be seen that the tearing force is large and it is not suitable for actual use. Example 2 Instead of SEBS- used in Example 1, a partially hydrogenated polystyrene-polybutadiene-polystyrene block copolymer compound (trade name: Elastomer Compound AR 800C, manufactured by Aron Kasei Co., Ltd., hereinafter abbreviated as SEBS-) was used, Example 1 except for (sample) where each is blended in the proportions shown in Table 3
I went in the same way. The results are shown in Table 4. It can be seen from Table 4 that all of the compositions have a good balance between tearing force and fusion strength.

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Claims (1)

[Claims] 1 Polypropylene (A): 20 to 90 parts by weight, density: 0.890 to 0.940 g/cm ³ , X-ray crystallinity: 10 to 64%, and melting point: 110 to 127°C, ethylene and carbon. Copolymer (C) with α-olefin number 4 to 20: 80 to 10 parts by weight, and polypropylene (A) + ethylene/α-olefin copolymer (C) = 100 parts by weight, monovinyl terminal The substituted aromatic hydrocarbon polymer block S constitutes 8 to 55% by weight of the block copolymer (D), at least two terminal monovinyl substituted aromatic hydrocarbon polymer blocks S and at least one intermediate conjugated diolefin polymer. Partial hydrogenation consisting of block B, in which not more than 25% of the aromatic double bonds of polymer block S and at least 80% of the aliphatic double bonds of conjugated diolefin polymer block B have been reduced by hydrogenation. Block copolymer (D): 1 or
100 parts by weight of a polypropylene composition.