JP4483537B2 - Multi-layer plastic container - Google Patents

Description

  The present invention relates to a multi-layer plastic container that has no deterioration in transparency when heated, is highly rigid, and has excellent impact resistance at low temperatures.

  2. Description of the Related Art Conventionally, a multi-layer plastic container including a gas barrier intermediate layer as a container for food or medicine and having an olefin resin layer disposed at least on an outer layer or an inner layer is known. As the olefin resin used for the outer layer or the inner layer, a polypropylene resin is often used because heat resistance and transparency are obtained.

  This type of multi-layer plastic container is slightly inferior to glass bottles, but has excellent drop strength, but the drop strength at low temperatures is not sufficient, and a low-temperature container filled with contents is accidentally dropped. If you let it go, it could be damaged.

  When the outer layer or inner layer of a multilayer plastic container is composed of a polypropylene resin alone, it is difficult to obtain a container having a good balance of transparency, impact resistance, cold resistance, rigidity, etc. Various proposals have been made to improve the properties by blending rich polyethylene-based resins and other elastomers. (For example, see Patent Documents 1 to 4)

JP-A-6-72424 Japanese Patent Application Laid-Open No. 7-195952 JP 2003-226323 A JP 2003-291935 A

  In Patent Document 1, in order to improve the cold resistance of a multilayer bottle having a gas barrier resin intermediate layer, the outermost layer of the container is made of polypropylene resin with a density of 0.890 to 0.915 (g / cc). A multilayer bottle constituted by a resin composition containing a linear ultra-low density polyethylene resin is proposed. However, in this multilayer bottle, it is difficult to obtain a high-rigidity bottle because the flexural modulus at room temperature is low.

In Patent Document 2, the outermost layer of the container is crystallized at a density of 0.890 to 0.925 g / cm ³ in 80 to 99% by weight of a propylene / α-olefin copolymer having a crystal melting point of 140 to 160 ° C. A high-gloss multilayer hollow container composed of an olefin polymer composition having a melt flow rate (MFR) of 2 to 30 g / 10 min, comprising 20 to 1% by weight of a linear low density polyethylene having a melting point of 110 to 125 ° C. has been proposed. Yes. However, even this multi-layer hollow container is not always satisfactory in terms of rigidity and impact resistance at low temperatures.

  In recent years, “hot pack type” foods and beverages that heat containers to about 65 to 90 ° C. at the time of filling or after filling contents into plastic containers such as bottles are widely used. The pack-type plastic container has a problem that when the contents are filled and heated, the container is whitened and transparency is lowered. This problem is particularly remarkable in a plastic container having a resin layer in which a flexibility-imparting component such as an ultra-low density polyethylene resin is blended with a polypropylene resin, and improvement has been demanded.

  Therefore, the present invention eliminates the above-mentioned problems of the prior art, provides a balanced balance of properties such as transparency, impact resistance at low temperatures, and rigidity, and can maintain transparency and rigidity even during heating. The object is to provide a plastic container.

  As a result of intensive studies, the present inventors have determined that at least one resin layer of the multilayer plastic container is made of a polypropylene resin having specific properties, a first ultra-low density polyethylene resin having specific properties, and a specific property. The present invention has been completed by finding that the above-mentioned problems can be solved by using a resin composition containing a combination of a second ultra-low density polyethylene resin having properties.

That is, the present invention employs the following configurations 1 to 8.
1. (A) Polypropylene resin having a flexural modulus of 800 to 1200 MPa at room temperature and a crystallization heating value of 60 to 90 mJ / mg, (B) a density of 0.900 to 0.920 g / cm ³ and a melting point of 95 to A first ultra-low density polyethylene resin having a temperature of 120 ° C. and (C) a second ultra-low density polyethylene resin having a density of 0.880 to 0.900 g / cm ³ and a melting point of 65 to 90 ° C. And (A) a multilayer plastic comprising at least one resin layer composed of a resin composition containing 3 to 20 parts by weight of (B) and (C) in total with respect to 100 parts by weight container.
2. 2. The resin composition according to 1, wherein 1 part by weight or more of (C) the second ultra-low density polyethylene resin is blended with 100 parts by weight of the polypropylene resin (A). Multi-layer plastic container.
3. When the blending ratio of (B) first ultra-low density polyethylene resin and (C) second ultra-low density polyethylene resin in the resin composition is (B) + (C) = 100 parts by weight (B) 5 to 95 parts by weight (C) 95 to 5 parts by weight The multilayer plastic container according to 1 or 2,
4). Resin containing at least one of the main layer or inner layer of the multilayer plastic container includes (A) polypropylene resin, (B) first ultra-low density polyethylene resin, and (C) second ultra-low density polyethylene resin. 4. The multilayer plastic container according to any one of 1 to 3, which is composed of a composition.
5). The multilayer plastic container according to any one of 1 to 4, wherein the multilayer plastic container has a gas barrier resin intermediate layer.
6). 6. The multilayer plastic container according to 5, wherein the gas barrier resin intermediate layer is composed of a resin selected from a saponified ethylene / vinyl acetate copolymer, a polyamide resin, and a cyclic olefin resin.
7). The multilayer plastic container comprises a resin composition containing the recovered resin (A) polypropylene resin, (B) first ultra-low density polyethylene resin and (C) second ultra-low density polyethylene resin. The multilayer plastic container according to any one of 1 to 6, which has a main layer.
8). In order from the outer layer side, the multilayer plastic container is an outer layer / adhesive resin layer / gas barrier resin intermediate layer / adhesive resin layer / adhesive resin layer / (A) polypropylene resin composed of at least one polyolefin resin composition. B) a main layer composed of a resin composition containing a first ultra-low density polyethylene resin and (C) a second ultra-low density polyethylene resin / an inner layer composed of at least one polyolefin resin composition. The multilayer plastic container according to any one of 1 to 7, which has a layer structure as follows.
9. The multilayer plastic container comprises, in order from the outer layer side, an outer layer composed of at least one polyolefin resin composition / (A) polypropylene resin, (B) first ultra-low density polyethylene resin, and (C) second. Main layer / adhesive resin layer / gas barrier resin intermediate layer / adhesive resin layer / (A) polypropylene resin, (B) first ultra-low density polyethylene resin It has a layer structure comprising a main layer composed of a resin composition containing a low density polyethylene resin and (C) a second ultra-low density polyethylene resin / an inner layer composed of at least one polyolefin resin composition. The multilayer plastic container according to any one of 1 to 7,
10. The multilayer plastic container according to any one of 1 to 9, wherein the multilayer plastic container is a hollow container that undergoes a heating treatment at 65 to 90 ° C. at the time of filling the contents or after filling.

  According to the present invention, it is possible to obtain a multilayer plastic container which is excellent in transparency and has a good balance of properties such as impact resistance at low temperatures and rigidity. The multilayer plastic container of the present invention prevents the container from being whitened to reduce transparency and rigidity, even when the container is heated to about 65 to 90 ° C. when filling the contents or after filling. It has a very high practical value.

In the present invention, at least one resin layer of a multilayer plastic container is composed of (A) a polypropylene resin having a flexural modulus of 800 to 1200 MPa at room temperature and a crystallization heating value of 60 to 90 mJ / mg, (B) density Of 0.900 to 0.920 g / cm ³ and a melting point of 95 to 120 ° C. (hereinafter abbreviated as “VLDPE1”), and (C) a density of 0.880 to Containing a second ultra-low density polyethylene-based resin (hereinafter abbreviated as “VLDPE2”) having a melting point of 65 to 90 ° C. at 0.900 g / cm ³ , (A) with respect to 100 parts by weight of (B) And (C) is comprised by the resin composition (henceforth "the resin composition of this invention") which mix | blended 3-20 weight part in total, It is characterized by the above-mentioned.

  In the present invention, the crystallization calorific value of the resin used is measured according to JIS K7122, and the flexural modulus is a value measured according to JIS K7171.

  Examples of the (A) polypropylene resin that is the main component of the resin composition of the present invention include polypropylene and propylene / α-olefin copolymers obtained by copolymerizing propylene and α-olefins such as ethylene. Examples of such copolymers include propylene / ethylene random copolymers and propylene / ethylene block copolymers. These polypropylene resins can be used alone or in combination of two or more.

Among these, a propylene / ethylene random copolymer is preferable in terms of transparency, and in particular, a propylene / ethylene random copolymer having an ethylene content of about 1.0 to 4.5% by weight is preferable in terms of transparency and rigidity. Preferably used.
If the ethylene content of the propylene / ethylene random copolymer used is less than 1.0% by weight, the transparency of the resulting multilayer container may be lowered depending on the molding conditions. Further, when the ethylene content exceeds 4.5% by weight, the rigidity of the resulting container can be maintained when the resin composition of the present invention is mixed with VLDPE1 and VLDPE2 to produce a multilayer plastic container. There may not be.

(B) VLDPE1 constituting the resin composition of the present invention has a density of 0.900 to 0.920 g / cm ³ and a melting point of 95 to 120 ° C. in terms of transparency and impact resistance of the multilayer plastic container. Use what is.
Further, (C) VLDPE2 constituting the resin composition of the present invention has a density of 0.880 to 0.900 g from the viewpoints of low temperature impact resistance, rigidity, and transparency during heating of the multilayer plastic container. / Cm ³ and a melting point of 65 to 90 ° C. is used. When the melting point of VLDPE2 is less than 65 ° C, the container becomes cloudy when the contents are heated and filled usually at 65 ° C or higher. Therefore, by using VLDPE2 having a melting point higher than the filling temperature of the contents, it is possible to obtain a multilayer plastic container in which transparency is not impaired during warm filling.

In the resin composition of the present invention, 3 to 20 parts by weight of (B) VLDPE1 and (C) VLDPE2 are added to 100 parts by weight of (A) polypropylene resin. In that case, it is preferable to blend 1 part by weight or more of (C) VLDPE2 with respect to 100 parts by weight of (A) polypropylene resin. Further, the blending ratio of (B) VLDPE1 and (C) VLDPE2 in the fat composition is (C) with respect to (B) 5 to 95 parts by weight when (B) + (C) = 100 parts by weight. The amount is preferably 95 to 5 parts by weight.
By setting each component constituting the resin composition to such a blending ratio, a multilayer plastic container having the desired properties can be obtained.
The resin composition of the present invention is suitably used as a resin constituting at least one main layer or inner layer of a multilayer plastic container.

The layer structure of the multilayer plastic container of the present invention is not particularly limited, but it is preferable to provide an intermediate layer composed of a gas barrier resin. The resin constituting the gas barrier resin intermediate layer is not particularly limited. For example, saponified ethylene / vinyl acetate copolymer, polyamide resin, cyclic olefin resin, and the like can be used.
A suitable material constituting the gas barrier resin intermediate layer includes a saponified ethylene / vinyl acetate copolymer having an ethylene content of 20 to 50 mol% and a saponification degree of 97 mol% or more. Particularly, those having an MFR measured at 210 ° C. of 3.0 to 15.0 g / 10 min are preferably used.

Other gas barrier resins include polyamides having 3 to 30 amide groups per 100 carbon atoms, especially 4 to 25 polyamides, polyamides having aromatic rings, cyclic olefin copolymer resins, poly Acrylonitrile, a high-density aliphatic polyester having a density of 1.5 or more, such as a polyglycolic acid copolymer, is used.
These gas barrier resins can be used alone or in admixture of two or more, and other thermoplastic resins may be mixed within a range not impairing the properties thereof.

  This cyclic olefin copolymer resin is a polyolefin-based resin consisting only of hydrogen and carbon, and has a main chain skeleton or side chain with factors such as a cyclic structure that inhibits the crystal structure and a bulky structure. A polyolefin-based cyclic polyolefin copolymer having a cyclic polyolefin component in the main chain skeleton is preferably used.

The cyclic olefin component, for example, bicyclo (2.2.1) hept-2-ene or derivatives thereof, tetracyclo ^(4.4.0.1 2,5 ^.1 7,10) -3- dodecene or a derivative thereof, hexacyclo ^{(6.6.1.1 3,6 .1 10,13 .0 2,7 .0} 9,14) -4- heptadecene or derivatives thereof, octacyclo ^(8.8.0.1 2,9 .1 ^4,7 .1 ^11,10 .1 ^13,16 .0 ^3,8 .0 ^12,17) -5- docosenoic or derivatives thereof, pentacyclo ^(6.6.1.1 3,6 ^{.0 2,7.} 0 ^9,14) -4- hexadecene or derivatives thereof, pentacyclo ^{(6.5.1.1 3,6 .0 2,7 .0 9,13)} -4- pentadecene or derivatives thereof, heptacyclo (8.7. 0.1 ^2,9 .1 ^4,7 .1 ^11,16 .0 ^3,8 .0 ^12,16) -5-heneicosene or derivatives thereof, tricyclo ^(4.4.0.1 2, 5)-3-undecene or derivatives thereof, tricyclo (4.3 .0.1 ^2,5) -3-decene or derivatives thereof, pentacyclo ^{(6.5.1.1 3,6 .0 2,7 .0 9,13)} -4,10- penta decadiene or a derivative thereof , pentacyclo ^{(4.7.0.1 2,5 .0 8,13 .1 9,12)} -3- pentadecene or derivatives thereof, heptacyclo ^(7.8.0.1 3,6 ^{.0 2,7.} 1 ^10,17 .0 ^11,16 .1 ^12,15) -4-eicosene or derivatives thereof, Nonashikuro ^{(9.10.1.1 4,7 .0 3,8 .0 2,10 .0} 12,21 .1 ^13,20 .0 ^{14 and 19} .1 ^{1 ,} Can be mentioned 19) -5 Pentasekon or a derivative thereof.

  Examples of the polyolefin component containing the cyclic olefin component include ethylene and propylene, 1-butene, 1-pentene, 4-methyl-pentene, 3-methyl-pentene, 1-hexene, 1-heptene and 1-octene. , 1-nonene, 1-decene, and the like, and may be a homopolymer composed of one component or a copolymer composed of two or more components. In the cyclic polyolefin copolymer containing the cyclic olefin component, the structural unit derived from the ethylene component is in the range of 40 to 95 mol%, preferably 50 to 80 mol%, and the structural unit derived from the cyclic polyolefin component is 1 mol%. Although it is effective from the addition, the range of usually 5 to 60 mol%, preferably 20 to 50 mol% is appropriate, and structural units derived from olefin components such as ethylene components are randomly arranged to form a cyclic polyolefin copolymer. Forming.

The multilayer plastic container of the present invention can be further provided with one or more outer layers and inner layers made of a thermoplastic resin. There is no restriction | limiting in particular in the material which comprises such a layer, Any thermoplastic resin normally used for a plastic container can be used.
Preferred thermoplastic resins include polyolefin resins such as low-, medium-, or high-density polyethylene, polypropylene, propylene / α-olefin copolymers such as propylene / ethylene copolymers, ethylene / vinyl acetate copolymers. Polymer (EVA), ethylene / ethyl acrylate copolymer (EEA), olefin resin graft-modified with ethylenically unsaturated carboxylic acid or its anhydride, ion-crosslinked olefin copolymer (ionomer), cyclic olefin component The contained polyolefin or the like is used.

  Particularly preferable polyolefin-based resins include propylene homopolymers or propylene as a main component, and ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-tetradecene, 1 -The propylene * alpha-olefin random copolymer, the block copolymer, or the graft copolymer which copolymerized C2-C20, such as octadecene, Preferably it is 2-10. These polyolefin resin can be used individually or in mixture of 2 or more types.

  Low-density ethylene / α-olefin copolymer (m-VLL) polymerized with hexene-1 as a comonomer using a metallocene catalyst to further improve impact resistance in the polyolefin resin layer, petroleum A highly flexible resin component such as a resin or hydrogenated petroleum resin may be added.

  In the multilayer plastic container of the present invention, a recovered resin obtained by regrinding burrs or defective products generated in the production of the multilayer plastic container in the resin composition of the present invention or in the polyolefin resin constituting the outer layer or the inner layer. Can be blended. The amount of the recovered resin in these resin layers is preferably 70% by weight or less based on the entire resin composition constituting the resin layer.

  As the recovered resin to be blended in the resin layer such as the main layer, a resin containing a gas barrier resin and an adhesive resin derived from a multilayer plastic container can be used. The resin layer containing the recovered resin can be provided in one layer or two or more layers in the multilayer plastic container, and is usually preferably provided at a position adjacent to the gas barrier resin intermediate layer via the adhesive resin layer.

  In each resin layer constituting the multilayer plastic container of the present invention, various crystal nucleating agents, lubricants composed of higher fatty acid amides such as oleic acid amide, erucic acid amide, etc., and plastic containers are usually used as necessary. Additives such as added ultraviolet absorbers, antistatic agents, colorants such as pigments, antioxidants and neutralizing agents can be blended.

As the crystal nucleating agent, an aromatic carboxylic acid metal salt, an aromatic phosphate metal salt, a sorbitol derivative, a rosin metal salt, a metal salt of an aromatic phosphorus compound, or the like is used. Preferred crystal nucleating agents include aluminum Pt-butylbenzoate, sodium 2,2′-methylenebis (4,6-di-t-butylphenyl) phosphate, 2,2′-methylenebis (4,6 phosphate). -Di-t-butylphenyl) aluminum, p-ethylbenzylidene sorbitol, sodium salt of rosin and the like.
The compounding amount of these crystal nucleating agents is 0.05 to 0.5% by weight, preferably 0.2 to 0.3% by weight, based on the resin constituting the resin composition.

An adhesive resin can be interposed between the resin layers constituting the multilayer plastic container of the present invention as necessary.
Examples of such adhesive resins include ethylene / α-olefin copolymer obtained by copolymerizing ethylene and propylene, 1-butene, 1-pentene, 1-heptene, 1-octene, and other α-olefins having up to 10 carbon atoms. It is preferable to use a resin obtained by graft-modifying the union with an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid or crotonic acid, or an anhydride thereof.

The graft modification rate of these adhesive resins is preferably about 0.05 to 5% by weight. These acid-modified ethylene / α-olefin copolymers can be used alone or in admixture of two or more. In addition, an ethylene / α-olefin copolymer modified with a high concentration of acid in advance and an unmodified low density polyethylene, ethylene / vinyl acetate copolymer, ethylene / α-olefin copolymer, polyolefin such as high density polyethylene It is also preferable to use, as an adhesive resin, a blend obtained by blending a resin and adjusting the acid modification rate of the entire resin to about 0.05 to 5% by weight.
When the acid modification rate is less than 0.05% by weight, the adhesiveness is insufficient, and delamination may occur during handling of the preform, blow molding, or product. On the other hand, when the acid modification rate exceeds 5% by weight, the cost required for modification is increased and the productivity is remarkably lowered, foaming is likely to occur during blow molding, and the molding range becomes extremely narrow. Will occur.

  As a preferable layer structure of the multilayer plastic container of the present invention, an outer layer / adhesive resin layer / gas barrier resin intermediate layer / adhesiveness composed of at least one polyolefin resin composition in order from the outer layer side of the multilayer plastic container. A layer structure comprising a resin layer / a main layer composed of the resin composition of the present invention / an inner layer composed of at least one polyolefin resin composition, and at least one polyolefin resin in order from the outside of the multilayer plastic container Outer layer constituted by the composition / main layer constituted by the resin composition of the present invention / adhesive resin layer / gas barrier resin intermediate layer / adhesive resin layer / main layer constituted by the resin composition of the present invention / at least 1 What has the layer structure which consists of an inner layer comprised with the polyolefin-type resin composition of the layer is mentioned.

As a specific example of such a layer structure, the resin of the present invention containing an outer resin layer / adhesive resin layer / gas barrier resin intermediate layer / adhesive resin intermediate layer / recovered resin made of the first polypropylene resin Resin layer made of composition / inner resin layer made of first polypropylene resin; outer resin layer made of first polypropylene resin / adhesive resin layer / gas barrier resin intermediate layer / adhesive resin intermediate layer / recovery Resin layer comprising resin composition of the present invention containing resin / inner resin layer comprising second polypropylene resin; outer resin layer comprising first polypropylene resin / adhesive resin layer / gas barrier resin intermediate layer / Adhesive resin intermediate layer / Resin layer comprising the resin composition of the present invention containing the recovered resin / Inner resin layer comprising the resin composition of the present invention; comprising the first polypropylene resin From the resin composition of the present invention containing a resin layer / adhesive resin layer / gas barrier resin intermediate layer / adhesive resin intermediate layer / recovered resin comprising the resin composition of the present invention containing a layer resin layer / recovered resin Resin layer / inner layer resin layer made of first polypropylene resin; outer layer resin layer made of first polypropylene resin / resin layer made of resin composition of the present invention containing recovered resin / adhesive resin layer / gas Barrier resin intermediate layer / adhesive resin intermediate layer / resin layer comprising the resin composition of the present invention containing the recovered resin / inner layer resin layer comprising the second polypropylene resin; outer resin comprising the first polypropylene resin Layer / resin composition comprising the resin composition of the present invention containing a recovered resin / adhesive resin layer / gas barrier resin intermediate layer / adhesive resin intermediate layer / resin composition of the present invention containing a recovered resin A resin layer having a high flexibility in the first polypropylene resin layer or the second polypropylene resin constituting the outer layer or the inner layer in these layer configurations. Are appropriately blended; and the like.

  In these examples, as the first polypropylene resin used for the outer layer, it is desirable to use a propylene / α-olefin random copolymer having a high MFR and high glossiness and high transparency. In addition, as the second polypropylene resin used only for the inner layer, a propylene / α-olefin random copolymer having a small MFR should be used in order to improve moldability and impact resistance while having high transparency. It is preferable that the resin composition of the present invention can also be used as the second polypropylene resin.

In the multilayer plastic container of the present invention, the outer layer and the inner layer can be composed of the same polyolefin resin composition, but the outer layer and the inner layer are preferably composed of different polyolefin resin compositions.
The required properties for the resin constituting the layer are often very different between the outer layer that greatly affects the appearance and transportability of the multilayer plastic container and the inner layer that is in direct contact with the contents of the container. In particular, when the contents are foods and beverages, there is a large difference in the required properties for the resins that make up the outer and inner layers, making it very difficult to apply a common resin composition and a special manufacturing process is required. There are problems such as high manufacturing costs.
On the other hand, when the outer layer and inner layer of the multilayer plastic container are made of different polyolefin resins, the resin can be selected in consideration of the required resin characteristics and price, so a more rational layer structure can be obtained. It can be set as the container which has.

On the other hand, the resin composition of the present invention used for constituting the main layer can be used as a resin constituting the inner layer, and in this case, the main layer and the inner layer can be constituted by the same resin composition. Often preferred.
The main layer of the multilayer plastic container and the inner layer that is in direct contact with the contents of the container, although there are differences depending on the presence or absence of direct contact with the contents of the container, other required characteristics are approximate, and the container contents Both layers can be made of the same resin composition by selecting a resin composition in consideration of the point of direct contact with respect to.

EXAMPLES Next, the present invention will be further described with reference to examples, but the following specific examples are not intended to limit the present invention.
In the following examples, a parison obtained by co-extrusion of a multilayer multiple die by a conventional method was directly blow-molded by a rotary blow molding machine to mold a multilayer plastic bottle having a container weight of 26 g and an internal volume of 600 cc.

Example 1
(A) With respect to 100 parts by weight of a propylene-ethylene random copolymer having a flexural modulus of 800 MPa at room temperature and a crystallization exotherm of 60 mJ / mg, (B) a density of 0.905 g / cm ³ and a melting point of 95 ° C. 9 parts by weight of a linear ultra-low density polyethylene resin (VLDPE1) and (C) 9 parts by weight of VLDPE2 having a density of 0.885 g / cm ³ and a melting point of 69 ° C. A product (resin composition of the present invention) was prepared.
In order from the outer layer of the multilayer plastic container, an outer resin layer comprising a first propylene / ethylene random copolymer having a thickness of 100 μm and a density of 0.9 g / cm ³ , MFR 9.0 g / 10 min and an ethylene content of 7 mol%; An adhesive resin layer comprising a maleic anhydride-modified polypropylene polymer having a thickness of 10 μm and a density of 0.9 g / cm ³ , an MFR of 3.5 g / 10 minutes and a maleic anhydride content of 0.3% by weight; A gas barrier resin layer comprising a saponified ethylene / vinyl acetate copolymer having an ethylene content of 32 mol% and a saponification degree of 99.5%; the adhesive resin layer having a thickness of 10 μm; and the above having a thickness of 315 μm. Recovered resin that regrinds defective products and burrs that occur during blow molding of polypropylene and polyethylene resin compositions and multilayer plastic bottles 5 types and 6 layers multilayer bottles having a layer structure comprising: a main layer resin layer composed of a resin composition mixed at a weight ratio of 50/50; an inner layer resin layer composed of the above-described polypropylene / polyethylene resin composition having a thickness of 50 μm; Was made.

(Example 2)
In Example 1, as a polypropylene / polyethylene resin composition constituting the main layer resin layer and the inner resin layer, instead of the (A) polypropylene / ethylene random copolymer used in Example 1, a flexural modulus of 900 MPa, A multilayer plastic bottle was produced in the same manner as in Example 1 except that a polypropylene / ethylene random copolymer having a crystallization exotherm of 65 mJ / mg was used.

(Example 3)
In Example 1, instead of the polypropylene / ethylene random copolymer (A) used in Example 1 as a polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer, a flexural modulus of 980 MPa, A multilayer plastic bottle was produced in the same manner as in Example 1 except that a polypropylene / ethylene random copolymer having a crystallization heat generation amount of 71 mJ / mg was used.

Example 4
In Example 1, in place of the polypropylene / ethylene random copolymer (A) used in Example 1 as the polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer, the flexural modulus was 1100 MPa, A multilayer plastic bottle was produced in the same manner as in Example 1 except that a polypropylene / ethylene random copolymer having a crystallization exotherm of 80 mJ / mg was used.

(Example 5)
In Example 1, as the polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer, (B) instead of the polypropylene / ethylene random copolymer used in Example 1, a flexural modulus of 1200 MPa, A multilayer plastic bottle was produced in the same manner as in Example 1 except that a polypropylene / ethylene random copolymer having a crystallization exotherm of 90 mJ / mg was used.

(Comparative Example 1)
In Example 1, as a polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer, (A) instead of the polypropylene / ethylene random copolymer used in Example 1, a flexural modulus of 700 MPa, A multilayer plastic bottle was produced in the same manner as in Example 1 except that a polypropylene / ethylene random copolymer having a crystallization exotherm of 57 mJ / mg was used.

(Comparative Example 2)
In Example 1, instead of the polypropylene / ethylene random copolymer (A) used in Example 1 as the polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer, the flexural modulus 1350 MPa, A multilayer plastic bottle was produced in the same manner as in Example 1 except that a polypropylene / ethylene random copolymer having a crystallization exotherm of 98 mJ / mg was used.

  Table 1 shows the results of evaluating the compression strength, the low temperature drop strength, and the heating suitability (transparency) of the multilayer plastic bottles obtained in Examples 1 to 5 and Comparative Examples 1 and 2 as follows. .

(Compressive strength)
The bottle was allowed to stand in an upright state, and the maximum compressive strength was measured at a compression speed of 50 mm / min using an orientec Tensilon universal testing machine UCT-500.

(Low temperature drop strength)
Fill a plastic bottle with 600 cc of saturated saline and store it in a refrigerator at 0 ° C, -5 ° C or -10 ° C for 24 hours, then remove it from the height of 1.0m on the concrete surface (bottom bottom down) ) And dropped to confirm the number of breaks. The numbers in the table indicate the number of breakage when 10 multilayer plastic bottles are used and dropped 10 times at the maximum.

(Heating aptitude)
Immediately after each plastic bottle was immersed in warm water at 65 ° C. or 85 ° C. for 10 minutes, haze (cloudiness) was measured using NDH1001 manufactured by Nippon Denshoku Industries Co., Ltd. based on JIS K7136.

(transparency)
Based on JIS K7105, haze (cloudiness) was measured about each bottle using NDH1001 by Nippon Denshoku Industries.

In Table 1, the determination of ◯, ×, △ means the following evaluation. (Same for other tables)
◯: Good △: No problem in use, but slightly inferior ×: Problem in use Note that the low temperature drop strength was determined for the low temperature drop test result at 0 ° C. (Same for other tables)

  As seen in Table 1, in Examples 2 to 5 in which the flexural modulus of the polypropylene / ethylene random copolymer (A) constituting the polypropylene / polyethylene resin composition is 900 to 1200 MPa, the compression strength is good. there were. Even in Example 1 where the flexural modulus is 800 MPa, the compressive strength is slightly lower than in Examples 2 to 5, but there is no practical problem. In Examples 1 to 5, bottles having high rigidity and excellent impact resistance were obtained.

  On the other hand, in Comparative Example 1 in which the flexural modulus of the polypropylene / ethylene random copolymer (A) constituting the polypropylene / polyethylene resin composition is 700 MPa, the compressive strength is greatly reduced and the flexural modulus is 1350 MPa. In Comparative Example 2, the glass-like cracks whose origin was not specified in the low temperature drop strength at 0 ° C. frequently occurred, and all 10 bottles were broken.

In Examples 1 to 4, where the crystallization calorific value of the polypropylene / ethylene random copolymer constituting the polypropylene / polyethylene resin composition is 60 to 80 mJ / mg, the heating suitability (transparency) was good. It was. In Example 5 where the crystallization heat generation amount is 90 mJ / mg, the haze is slightly higher than in Examples 1 to 4, but there is no practical problem. In Examples 1-5, the bottle excellent also in transparency was obtained.
On the other hand, in Comparative Example 2 in which the heat generation of crystallization of the polypropylene / ethylene random copolymer (A) constituting the polypropylene / polyethylene-based resin composition is 98 mJ / mg, it does not matter whether it is heated at room temperature or 65 ° C. Therefore, the transparency was low enough to be visually confirmed, and the bottle had a remarkably high haze value.

(Example 6)
In Example 3, as the polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer, (A) 2 parts by weight of VLDPE1 is blended with 100 parts by weight of the polypropylene / polyethylene resin, (C) A multilayer plastic bottle was used in the same manner as in Example 3 except that the resin composition containing 1 part by weight of VLDPE2 was used.

(Example 7)
In Example 3, 14 parts by weight of (B) VLDPE1 is blended with respect to 100 parts by weight of (A) polypropylene / polyethylene resin as a polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer. (C) A multilayer plastic bottle was used in the same manner as in Example 3 except that the resin composition having 6 parts by weight of VLDPE2 was used.

(Example 8)
In Example 3, as the polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer, (A) 3 parts by weight of VLDPE1 with respect to 100 parts by weight of polypropylene / polyethylene resin, (C) A multilayer plastic bottle was used in the same manner as in Example 3 except that the resin composition having a blending amount of VLDPE2 of 17 parts by weight was used.

Example 9
In Example 3, as the polypropylene / polyethylene resin composition constituting the main layer resin layer and the inner resin layer, (A) 1 part by weight of the blending amount of VLDPE1 with respect to 100 parts by weight of the polypropylene / polyethylene resin, (C) A multilayer plastic bottle was used in the same manner as in Example 3 except that the resin composition in which the blending amount of VLDPE2 was 19 parts by weight was used.

(Example 10)
In Example 3, as the polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer, (A) 19 parts by weight of VLDPE1 is blended with respect to 100 parts by weight of the polypropylene / polyethylene resin, (C) A multilayer plastic bottle was used in the same manner as in Example 3 except that the resin composition containing 1 part by weight of VLDPE2 was used.

(Comparative Example 3)
In Example 3, as the polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer, (A) 20 parts by weight of VLDPE1 is blended with 100 parts by weight of the polypropylene / polyethylene resin, (C) A multilayer plastic bottle was used in the same manner as in Example 3 except that the resin composition having 6 parts by weight of VLDPE2 was used.

(Comparative Example 4)
In Example 3, as the polypropylene / polyethylene resin composition constituting the main layer resin layer and the inner resin layer, (A) 1 part by weight of the blending amount of VLDPE1 with respect to 100 parts by weight of the polypropylene / polyethylene resin, (C) A multilayer plastic bottle was used in the same manner as in Example 3 except that the resin composition in which the blending amount of VLDPE2 was 0.5 parts by weight was used.

  Table 2 shows the results of evaluating the compressive strength, the low temperature drop strength, and the heating suitability (transparency) of the multilayer plastic bottles obtained in Examples 3 and 6 to 10 and Comparative Examples 3 and 4.

  As can be seen from Table 2, (A) 100 parts by weight of polypropylene / polyethylene resin, (B) 2 parts by weight of VLDPE1 and (C) 1 part by weight of VLDPE2 blended resin composition was used. In No. 6, a bottle excellent in compressive strength and 65 ° C. heating suitability (transparency) was obtained. At low temperature drop strength at 0 ° C., 2 out of 10 pinholes were observed from the cramped portion. This example shows that the effect of the modifying material appears even in a small amount, and it can be determined that there is no practical problem in using at room temperature.

  On the other hand, in Comparative Example 4 using a resin composition obtained by blending (A) 100 parts by weight of polypropylene / polyethylene resin with 1 part by weight of (B) VLDPE1 and 0.5 part by weight of (C) VLDPE2. In the low temperature drop strength at 0 ° C., glassy cracks without specifying the starting point occurred frequently, and all 10 bottles were broken.

In Example 9 using a resin composition obtained by blending (A) 1 part by weight of (B) VLDPE1 and 19 parts by weight of (C) VLDPE2 with respect to 100 parts by weight of polypropylene / polyethylene resin, the compressive strength, 65 ° C. Although the heating aptitude (transparency) was slightly inferior, there was no practical problem, and a bottle excellent in low temperature drop strength at −5 ° C. and −10 ° C. was obtained.
On the other hand, in Example 10 using a resin composition in which 19 parts by weight of (B) VLDPE1 and 1 part by weight of (C) VLDPE2 were used, compressive strength, 65 ° C heating suitability (transparency), low temperature at 0 ° C A bottle with excellent drop strength was obtained.

(A) In Example 7 using a resin composition in which 14 parts by weight of (B) VLDPE1 and 6 parts by weight of (C) VLDPE2 were blended with 100 parts by weight of polypropylene / polyethylene resin, the compressive strength, A bottle excellent in warming suitability (transparency) and low temperature drop strength at −5 ° C. was obtained.
On the other hand, in Example 8 using a resin composition in which 3 parts by weight of (B) VLDPE1 and 17 parts by weight of (C) VLDPE2 were used, the compressive strength, 65 ° C. heating suitability (transparency) was slightly inferior. There was no problem in practical use, and a bottle excellent in low temperature drop strength at −5 ° C. and −10 ° C. was obtained.

  On the other hand, in Comparative Example 3 using a resin composition in which 20 parts by weight of (B) VLDPE1 and 6 parts by weight of (C) VLDPE2 were blended with respect to 100 parts by weight of (A) polypropylene-polyethylene resin, Although it was excellent in low temperature drop strength at -5 ° C, the compressive strength was remarkably reduced.

From Examples 3 and 6 to 10 and Comparative Examples 3 and 4 shown in Table 2, (A) VLDPE1 and (C) VLDPE2 blending ratios suitable for 100 parts by weight of polypropylene / polyethylene resin are as follows: The conditions (1) to (3) shown in FIG.
(1) 3 parts by weight ≦ VLDPE1 + VLDPE2 ≦ 20 parts by weight However, VLDPE2 contains 1 part by weight or more. (2) As VLDPE1 + VLDPE2 = 100 parts by weight 5 parts by weight ≦ VLDPE1 ≦ 95 parts by weight 95 parts by weight ≧ VLDPE2 ≧ 5 parts by weight (3) Particularly preferred conditions for maintaining rigidity, cold resistance (drop strength), and transparency (warming suitability) are:
15 parts by weight ≦ VLDPE1 ≦ 70 parts by weight 85 parts by weight ≧ VLDPE2 ≧ 30 parts by weight [However, the maximum condition satisfying (1) and (3) is
3 parts by weight ≦ VLDPE1 ≦ 14 parts by weight 17 parts by weight ≧ VLDPE2 ≧ 6 parts by weight The minimum condition satisfying (1) and (2) is as follows:
2 parts by weight ≦ VLDPE1
1 part by weight ≦ VLDPE2. ]
Among them, Example 3 using a resin composition in which 9 parts by weight of (B) VLDPE1 and 9 parts by weight of (C) VLDPE2 was blended with 100 parts by weight of (A) polypropylene / polyethylene resin It can be said to be the most suitable example which is very excellent in strength, 65 ° C. heating suitability (transparency) and low temperature drop strength at −5 ° C. and −10 ° C.

(Example 11)
In Example 3, the density of 0.883 g / cm ³ was used instead of VLDPE2 used in Example 3 as (C) VLDPE2 blended in the polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer. Thus, a multilayer plastic bottle was produced in the same manner as in Example 3 except that 9 parts by weight of VLDPE2 having a melting point of 65 ° C. was blended.

(Example 12)
In Example 3, the density of 0.892 g / cm ³ was used instead of VLDPE2 used in Example 3 as (C) VLDPE2 blended in the polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer. Then, a multilayer plastic bottle was produced in the same manner as in Example 3 except that 9 parts by weight of VLDPE2 having a melting point of 80 ° C. was blended.

(Example 13)
In Example 3, the density of 0.900 g / cm ³ was used instead of VLDPE2 used in Example 3 as (C) VLDPE2 blended in the polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer. Then, a multilayer plastic bottle was produced in the same manner as in Example 3 except that 9 parts by weight of VLDPE2 having a melting point of 90 ° C. was blended.

(Comparative Example 5)
In Example 3, the density of 0.875 g / cm ³ was used instead of VLDPE2 used in Example 3 as (C) VLDPE2 blended in the polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer. Thus, a multilayer plastic bottle was produced in the same manner as in Example 3 except that 9 parts by weight of VLDPE2 having a melting point of 60 ° C. was blended.

(Comparative Example 6)
In Example 3, instead of VLDPE2 used in Example 3, the density was 0.905 g / cm ³ as (C) VLDPE2 blended in the polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer. Thus, a multilayer plastic bottle was produced in the same manner as in Example 3 except that 9 parts by weight of VLDPE2 having a melting point of 95 ° C. was blended.

  Table 3 shows the results of evaluating the compressive strength, the low temperature drop strength, and the suitability for heating (transparency) of the multilayer plastic bottles obtained in Examples 3 and 11 and Comparative Examples 5 and 6.

  As can be seen from Table 3, in Examples 3 and 11 to 13 in which 9 parts by weight of (C) VLDPE2 having a melting point of 65 ° C. to 90 ° C. was blended with respect to the polypropylene / polyethylene resin composition, the compression strength and the low temperature drop strength were high. Both bottles were excellent. In Example 11 where the melting point of VLDPE2 is 65 ° C, the suitability for heating (transparency) at 65 ° C is slightly inferior, but there is no practical problem. In Example 13 where the melting point of VLDPE2 is 90 ° C. (> 85 ° C.), the suitability for heating at 85 ° C. is excellent, but Examples 3 and 11 and 12 where the melting point of VLDPE2 is 65 to 80 ° C. (<85 ° C.). Then, 85 degreeC heating aptitude (transparency) fell remarkably.

  On the other hand, in Comparative Example 5 where the melting point of VLDPE2 was 60 ° C. (<65 ° C.), the suitability for heating (transparency) at 65 ° C. was remarkably lowered and the compressive strength was also low. Further, in Comparative Example 6 where the melting point of VLDPE2 is 95 ° C., the heating aptitude (transparency) at 65 ° C. and 85 ° C. is both excellent and the compressive strength is good, but the starting point is low temperature drop strength at 0 ° C. Unspecified glassy cracks occurred frequently, and all 10 bottles were broken.

(Example 14)
In Example 3, the density of 0.920 g / cm ³ was used instead of VLDPE1 used in Example 3 as (B) VLDPE1 blended in the polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer. Thus, a multilayer plastic bottle was produced in the same manner as in Example 3 except that 9 parts by weight of VLDPE1 having a melting point of 115 ° C. was blended.

(Example 15)
In Example 3, (B) VLDPE1 blended in the polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer was replaced with VLDPE1 used in Example 3, and the density was 0.900 g / cm ^3. Then, a multilayer plastic bottle was produced in the same manner as in Example 3 except that 9 parts by weight of VLDPE1 having a melting point of 90 ° C. was blended.

(Comparative Example 7)
In Example 3, (B) VLDPE1 blended in the polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer was replaced with VLDPE1 used in Example 3, with a density of 0.890 g / cm ^3. Thus, a multilayer plastic bottle was produced in the same manner as in Example 3 except that 9 parts by weight of VLDPE1 having a melting point of 78 ° C. was blended.

(Comparative Example 8)
In Example 3, the density of 0.925 g / cm ³ was used instead of VLDPE1 used in Example 3 as (B) VLDPE1 blended in the polypropylene / polyethylene resin composition constituting the main resin layer and the inner resin layer. Then, a multilayer plastic bottle was produced in the same manner as in Example 3 except that 9 parts by weight of VLDPE1 having a melting point of 120 ° C. was blended.

  Table 4 shows the results of evaluating the compressive strength, the low temperature drop strength, and the heating suitability (transparency) of the multilayer plastic bottles obtained in Examples 3 and 14 and 15 and Comparative Examples 7 and 8.

As seen in Table 4, in Examples 3 and 14, and 15 in which 9 parts by weight of (B) VLDPE1 having a density of 0.900 to 920 g / cm ³ was blended with respect to the polypropylene / polyethylene resin composition, the compressive strength, It was obtained from a bottle excellent in both low temperature drop strength and 65 ° C. heating suitability (transparency). In Example 14 in which the density of VLDPE1 is 920 g / cm ³ , the low temperature drop strength at −5 ° C. is inferior to that in Examples 3 and 15, but there is no practical problem.

On the other hand, in Comparative Example 7 in which the density of VLDPE1 was 0.890 g / cm ³ , although the low temperature drop strength was excellent, the compressive strength and the 65 ° C. heating suitability (transparency) were significantly lowered. Further, in Comparative Example 8 in which the density of VLDPE1 is 0.925 g / cm ³ , the low temperature drop strength is remarkably reduced, and glassy cracks with unspecified starting points frequently occur in the low temperature drop test at 0 ° C. Five bottles were broken.

Claims (10)

(A) Polypropylene resin having a flexural modulus of 800 to 1200 MPa at room temperature and a crystallization heating value of 60 to 90 mJ / mg, (B) a density of 0.900 to 0.920 g / cm ³ and a melting point of 95 to A first ultra-low density polyethylene resin having a temperature of 120 ° C. and (C) a second ultra-low density polyethylene resin having a density of 0.880 to 0.900 g / cm ³ and a melting point of 65 to 90 ° C. And (A) a multilayer plastic comprising at least one resin layer composed of a resin composition containing 3 to 20 parts by weight of (B) and (C) in total with respect to 100 parts by weight container.   2. The resin composition according to claim 1, wherein 1 part by weight or more of (C) the second ultra-low density polyethylene resin is blended with 100 parts by weight of (A) polypropylene resin. The multilayer plastic container as described.   When the blending ratio of (B) first ultra-low density polyethylene resin and (C) second ultra-low density polyethylene resin in the resin composition is (B) + (C) = 100 parts by weight The multilayer plastic container according to claim 1, wherein (C) is 95 to 5 parts by weight with respect to (B) 5 to 95 parts by weight.   Resin containing at least one of the main layer or inner layer of the multilayer plastic container includes (A) polypropylene resin, (B) first ultra-low density polyethylene resin, and (C) second ultra-low density polyethylene resin. The multilayer plastic container according to any one of claims 1 to 3, wherein the multilayer plastic container is composed of a composition.   The multilayer plastic container according to any one of claims 1 to 4, wherein the multilayer plastic container has a gas barrier resin intermediate layer.   6. The multilayer plastic container according to claim 5, wherein the gas barrier resin intermediate layer is composed of a resin selected from saponified ethylene / vinyl acetate copolymer, polyamide resin, and cyclic olefin resin.   The multilayer plastic container comprises a resin composition containing the recovered resin (A) polypropylene resin, (B) first ultra-low density polyethylene resin and (C) second ultra-low density polyethylene resin. It has a main layer, The multilayer plastic container in any one of Claims 1-6 characterized by the above-mentioned.   In order from the outer layer side, the multilayer plastic container is an outer layer / adhesive resin layer / gas barrier resin intermediate layer / adhesive resin layer / adhesive resin layer / (A) polypropylene resin composed of at least one polyolefin resin composition. B) a main layer composed of a resin composition containing a first ultra-low density polyethylene resin and (C) a second ultra-low density polyethylene resin / an inner layer composed of at least one polyolefin resin composition. The multilayer plastic container according to claim 1, wherein the multilayer plastic container has a layer structure.   The multilayer plastic container comprises, in order from the outer layer side, an outer layer composed of at least one polyolefin resin composition / (A) polypropylene resin, (B) first ultra-low density polyethylene resin, and (C) second. Main layer / adhesive resin layer / gas barrier resin intermediate layer / adhesive resin layer / (A) polypropylene resin, (B) first ultra-low density polyethylene resin It has a layer structure comprising a main layer composed of a resin composition containing a low density polyethylene resin and (C) a second ultra-low density polyethylene resin / an inner layer composed of at least one polyolefin resin composition. A multilayer plastic container according to any one of claims 1 to 7. The multilayer plastic container according to any one of claims 1 to 9, wherein the multilayer plastic container is a hollow container that is subjected to a heating treatment at 65 to 90 ° C at the time of filling the contents or after filling.