JP2019155703A - Method for producing polyolefin multilayer sheet or film - Google Patents

Abstract

To provide a method for producing a polyolefin multilayer sheet or film comprising an outer layer having a uniform thickness of 2 to 50 μm, which is 1/40 to 1/100 of a total thickness, and a core layer thicker than this.SOLUTION: An outer layer of a polyolefin multilayer sheet or film has a thickness of 1/40 to 1/100 of a total thickness, 2 to 50 μm, and a thickness of a core layer is thicker than the outer layer. In a process of coextrusion, an extruder for forming the outer layer comprises a feed zone 2 and a compression zone 3 from an upstream, and a temperature T (°C) of the feed zone 2 satisfies a relationship of Tm-50°C≤T≤Tm-10°C (Tm is the melting point(°C) of a raw polyolefin.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a polyolefin multilayer sheet or film.

  It is known that a sheet or film has a multilayer structure in order to impart an excellent function. For example, polyolefins typified by polypropylene are useful as food containers because they have excellent physical properties and excellent hygiene. However, in order to improve the impact resistance at low temperatures, A structure has been proposed (for example, Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 10-157033 JP 2002-348421 A

  The inventors have come up with the idea that if the thickness of a specific layer can be made thinner, it may be possible to give the sheet or film a higher function. In general, when a multilayer sheet or film is produced through a co-extrusion step, the layer can be thinned by reducing the discharge rate of a molding machine for forming a specific layer. However, when forming an extremely thin layer, the discharge rate must be extremely reduced, and a thin layer cannot be formed under conventional molding conditions, or even if it can be formed, it is difficult to achieve a uniform thickness. there were. In view of such circumstances, the present invention is a polyolefin multilayer sheet comprising an outer layer having a uniform thickness of 1/40 to 1/100 of the total thickness and 2 to 50 μm and a core layer thicker than this. Alternatively, it is an object to provide a film.

The inventors have found that a polyolefin multilayer sheet or film having an outer layer having a uniform thickness of 2 to 50 μm can be produced by employing special molding conditions, and have completed the present invention. That is, the said subject is solved by the following this invention.
[1] A polyolefin multilayer sheet or film comprising an outer layer and a core layer and satisfying the following i) and ii):
i) The thickness of the outer layer is 1/40 to 1/100 of the total thickness, and is 2 to 50 μm. ii) The core layer is a manufacturing method that is thicker than the outer layer,
Coextruding the outer layer and the core layer to form a polyolefin multilayer sheet or film satisfying i) and ii),
An extruder for forming the outer layer in the co-extrusion step includes a feed zone and a compression zone from upstream,
The temperature T (° C.) of the feed zone satisfies the relationship of the formula (1).
Tm−50 ° C. ≦ T ≦ Tm−10 ° C. (1)
(Tm is the melting point (° C) of the raw material polyolefin)
Production method.
[2] The production method according to [1], further including a step of secondary processing the polyolefin multilayer sheet or film obtained in the coextrusion step so as to satisfy the above i) and ii).
[3] The production method according to [1] or [2], wherein the outer layer includes polypropylene containing 0 to 5.0% by weight of a comonomer selected from the group consisting of ethylene and C4 to C10-α-olefin.
[4] The polypropylene composition in which the core layer is:
Component (1) is a blend of a propylene homopolymer and a propylene copolymer containing a comonomer selected from the group consisting of ethylene and C4 to C10-α-olefin, the weight ratio of the two being 10 to 97 : 90 to 3 and the comonomer content in the blend is 3% by weight or less, and as component (2), 60 to 90% by weight of ethylene and one or more C3-C10-α-olefins An ethylene copolymer consisting of a copolymer with
The following (i) to (iii) are provided: (i) The weight ratio of the component (1): component (2) is 60 to 90:40 to 10
(Ii) MFR (230 ° C., load 2.16 kg) is 1.0 to 10 g / 10 min. (Iii) XSIV (xylene soluble intrinsic viscosity) is 0.5 to 2.0 dl / g,
The manufacturing method in any one of [1]-[3] containing.
[5] The manufacturing method according to [4], wherein the multilayer sheet or film includes three or more layers, and the outer layers are located on both outermost surfaces.
[6] The production method according to [5], wherein the multilayer sheet or film has a three-layer structure.
[7] The production method according to any one of [1] to [6], wherein the polypropylene composition has a phase structure in which the component (2) is dispersed in the component (1).
[8] The comonomer in the component (1) is ethylene,
The production method according to any one of [4] to [7], wherein the α-olefin in component (2) is propylene or butene-1.
[9] The production method according to any one of [3] to [8], wherein the comonomer in the polypropylene is ethylene.
[10] A multilayer sheet or film obtained by the production method according to any one of [1] to [9].

  According to the present invention, it is possible to provide a polyolefin multilayer sheet or film having an outer layer having a uniform thickness of 1/40 to 1/100 of the total thickness and 2 to 50 μm and a thicker core layer. .

It is a figure which shows the one aspect | mode of a screw structure.

  In the present invention, the sheet is a flat member (leaf-like member) having an overall thickness of 200 μm or more, and the film is a flat member (leaf-like member) having an overall thickness of less than 200 μm. Sheets or films are collectively referred to as “sheets”.

1. Manufacturing Method The present invention includes a step of coextruding and forming an outer layer having a specific thickness and a polyolefin multilayer sheet having a core layer thicker than the outer layer. The co-extrusion process is to form a molten resin using a plurality of extruders, pass each molten resin through a multilayer feed block or a multilayer manifold, etc. to form a multilayer structure, and cool and solidify this to form a molded product. It is a manufacturing process. Hereinafter, the co-extrusion step will be described.

(1) Process of forming outer layer In this invention, an outer layer is formed using the extruder provided with the screw structure provided with a feed zone and a compression zone from upstream. The raw material resin input side of the extruder is called upstream, and the die side is called downstream. FIG. 1 shows an embodiment of the screw configuration. In FIG. 1, 1 is a raw material resin inlet, 2 is a feed zone, 3 is a compression zone, and 4 is a metering zone.

The feed zone is a zone for transferring the raw material resin supplied from the raw material resin inlet to the downstream in a substantially solid state, and is also referred to as a solid phase zone. In the present invention, the temperature T (° C.) of the zone satisfies the relationship of the formula (1).
Tm−50 ° C. ≦ T ≦ Tm−10 ° C. (1)
In the formula (1), Tm is the melting point (° C.) of the raw material resin (raw material polyolefin). The lower limit value of T is preferably Tm-45 ° C, and more preferably Tm-40 ° C. The upper limit value of T is preferably Tm-20 ° C. When T is lower than Tm-50 ° C., the resin is not melted and sheet molding becomes difficult. When T is higher than Tm−10 ° C., the variation in the thickness of the outer layer in the width direction of the sheet or the like becomes large, resulting in overall appearance defects such as uneven gloss and transparency. Tm is the peak top temperature on the highest temperature side observed by second scanning the raw material resin using DSC. The second scan means that the raw material resin is heated and melted, cooled and crystallized, held at room temperature for 5 minutes, and then heated for the second time for thermal analysis. Specifically, 1) The raw material resin is heated to the melting temperature (230 ° C.), held at that temperature for 5 minutes, cooled to 30 ° C. at a temperature lowering rate of 10 ° C./min, held for 5 minutes, and 2) Heat analysis is performed up to 230 ° C. at a rate of temperature increase of 10 ° C./min. When polypropylene-based polyolefin is used as a raw material resin, T can be about 120 to 160 ° C. Although the length of a feed zone is adjusted suitably, when the length from the raw material injection position of a screw to a downstream end is set to L, it is preferable that a feed zone is 0.15L-0.3L length.

  The compression zone is a zone in which a solid phase resin is heated and compressed to a molten state. The temperature T ′ of the zone is appropriately adjusted, but is preferably Tm or higher. Specifically, when polypropylene-based polyolefin is used as a raw material resin, T ′ can be about 210 to 240 ° C. Although the length of a compression zone is adjusted suitably, it is preferable that it is 0.65-L. The compression zone may be provided with a so-called kneading zone that enables strong kneading. The compression zone and the feed zone are preferably adjacent.

  The metering zone is a zone for transferring the molten resin to the die. The temperature T ″ of the zone is appropriately adjusted, but is preferably equal to or higher than Tm, and may be the same as T ′. The length of the measurement zone is appropriately adjusted, but is 0.05 L to 0.2 L. Although other zones may be provided between the metering zone and the compression zone, the metering zone and the compression zone are preferably adjacent.

  The discharge amount of the extruder for the outer layer can be adjusted as appropriate depending on the thickness of the outer layer and the size of the sheet, but is preferably about 0.12 to 4.5 kg / hour, for example. In general, the smaller the diameter of the extruder, the more stably the resin can be extruded even at a lower discharge rate. However, since a space for melting and transporting the pellets charged as the raw material resin is necessary, the diameter is 20 mmφ. Making it smaller is not practical. On the other hand, in the extruder for core layers, the diameter is 30 mmφ to 90 mmφ for industrial use. In principle, it is possible to form an outer layer having a thickness of 1/40 to 1/100 of the total thickness based on the balance between the diameter of the outer layer extruder and the diameter of the core layer extruder. is there. However, under the conventional molding conditions, the discharge amount of the extruder for the outer layer is set to be small, so the discharge amount is not stable, the thickness variation in the width direction of the sheet etc. becomes large, and the appearance such as gloss unevenness as a whole Transparency deteriorates as defects occur. However, in the present invention, by setting the temperature of the feed zone in the extruder for the outer layer to the above-mentioned temperature, the resin can be efficiently transferred in the cylinder, so that the total thickness is 1/40 to 1/100, An outer layer having a thickness of 2 to 50 μm can be stably formed, and continuous production of a transparent sheet or the like having a good appearance is possible. When the thickness exceeds 50 μm, the impact resistance of the obtained polyolefin multilayer sheet or the like is lowered, and when it is less than 2 μm, the transparency of the polyolefin multilayer sheet or the like that can be difficult to stably form a thin outer layer is deteriorated. From this viewpoint, the upper limit of the thickness of the outer layer is preferably 40 μm or less, more preferably 35 μm or less, and further preferably 30 μm or less. The lower limit is preferably 4 μm or more, more preferably 8 μm or more, and further preferably 10 μm or more. Further, the thickness ratio is preferably 1/40 to 1/95, and more preferably 1/45 to 1/95.

  The present invention achieves the thickness conditions i) and ii) by coextrusion. Therefore, the manufacturing method of the present invention may include other processes such as secondary processing in addition to the co-extrusion process. Secondary processing will be described later.

  The polyolefin multilayer sheet or the like of the present invention has an outer layer of a layer (also referred to as “thin layer”) having a thickness of 1/40 to 1/100 of the total thickness and 2 to 50 μm, and a thicker layer (“thick layer”). As a core layer. Therefore, the outer layer is located on the outer side (surface side) of the core layer located at the center of the polyolefin multilayer sheet or the like. Therefore, when the polyolefin multilayer sheet of the present invention has three layers, the two outer layers (thin layers) become the outermost layers (outermost layers). When the polyolefin multilayer sheet of the present invention has four or more layers, it is preferable that at least one thin layer is the outermost layer (outermost layer). However, when the polyolefin multilayer sheet etc. of this invention are two layers, a thin layer is made into an outer layer and a thick layer is called a core layer for convenience.

(2) Step of forming the core layer The configuration and molding conditions of the extruder for forming the core layer are not particularly limited, the temperature may be a known temperature, and the discharge amount may be appropriately adjusted depending on the desired thickness. In one embodiment, the polyolefin multilayer sheet or the like of the present invention preferably has a three-layer structure of outer layer / core layer / outer layer. In the case of such a three-layer structure, the thickness ratio is generally set to 1: “5 to 20”: 1 in the conventional technique, but according to the present invention, the thickness ratio is set to 1: “40-100”: 1 can be set.

  One or more intermediate layers can be further provided between the outer layer / core layer, and the configuration and molding conditions of the extruder for forming the intermediate layer are also adjusted as appropriate. The intermediate layer is preferably thicker than the outer layer and thinner than the core layer, and the specific thickness is not limited, but may be, for example, 0.05 to 2 mm.

(3) Other Steps A polyolefin multilayer sheet or the like can be produced by laminating the molten resin obtained by the molding machine described above and cooling and solidifying it. The step of laminating may be as known, for example, a known multilayer feed block or multilayer manifold may be used. The step of cooling and solidifying the molded product may be as known, and examples include air cooling of the molded product and placing the molded product on a chill plate or the like. When placing on a chill plate or the like, the thickness of the molded product can be appropriately adjusted by adjusting the take-up speed. The molded product thus obtained, that is, a polyolefin multilayer sheet or the like is formed into a shape corresponding to the application and can be used for various applications.

  The polyolefin multilayer sheet obtained in this way can be used as a raw material, and further adjusted to a desired thickness as a stretched molded product by performing secondary processing such as vacuum forming, pressure forming, vacuum pressure forming, etc. it can. The secondary processing may be performed so as to satisfy the thickness conditions i) and ii) of the original fabric, or the secondary processing may be performed so as not to satisfy the conditions. However, considering the properties of the resulting polyolefin multilayer sheet, etc., the secondary processing is preferably carried out so that the polyolefin multilayer sheet after processing satisfies the thickness conditions i) and ii). That is, the manufacturing method of the present invention may include a step of secondary processing the raw fabric so as to satisfy the thickness conditions i) and ii). In this case, the actual thicknesses of the outer layer and the core layer do not vary or the thickness conditions i) and ii) are satisfied even if they vary. The secondary processed product thus obtained is not necessarily leaf-shaped, but the polyolefin multilayer sheet of the present invention includes the secondary processed product.

2. Polyolefin multilayer sheet etc. The polyolefin multilayer sheet etc. of this invention are comprised with polyolefin. Polyolefins used in the present invention include polypropylene, polyethylene, ethylene / propylene copolymer, ethylene / propylene / conjugated diene copolymer, ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer, ethylene -1-octene copolymer, propylene / 1-butene copolymer, propylene / 1-hexene copolymer, propylene / 1-octene copolymer and the like. The polypropylene may be homopolypropylene (propylene homopolymer), random polypropylene (propylene random copolymer), or block polypropylene. Here, the block polypropylene is sometimes called a heterophasic copolymer, heterophasic polypropylene, impact-resistant propylene polymer, or impact-resistant polypropylene polymer, and includes a rubber component obtained by copolymerization or mixing. Polypropylene. The polyethylene may be any of ultra-low density polyethylene, low density polyethylene, linear low density polyethylene, medium density polyethylene, and high density polyethylene. Polyolefin may be used individually by 1 type and may use 2 or more types together. Among the above polyolefins, polypropylene is preferable in that the effect of the present invention is particularly exhibited. Since these polyolefin multilayer sheets and the like are all excellent in transparency and cold shock resistance, they are useful as packaging materials, container materials, particularly food containers. Since the thickness and position of each layer are as described above, preferred materials constituting each layer will be described below.

(1) Outer layer The outer layer preferably contains polypropylene containing 0 to 5.0% by weight of a comonomer selected from the group consisting of ethylene and C4 to C10-α-olefin. In particular, a propylene homopolymer or a propylene random copolymer is preferably included. In the propylene random copolymer, the comonomer content may be 5.0% by weight or less, but is preferably 4.0% by weight or less. When the amount of the comonomer exceeds the upper limit, the production stability of the obtained sheet or the like is lowered. The lower limit of the comonomer content in the propylene random copolymer may be more than 0% by weight, but is preferably 0.1% by weight or more. Propylene homopolymers and propylene random copolymers can be produced by known methods. As the comonomer in the propylene random copolymer, ethylene is preferable from the viewpoint of being industrially inexpensive and stably distributed and relatively easily available. The polypropylene preferably has an MFR of 1.0 to 10 g / 10 min (measured at 230 ° C. and a load of 2.16 kg). If the MFR exceeds the upper limit value, it becomes difficult to draw down at the time of molding, so that it is difficult to produce a sheet or the like.

  A composition obtained by adding a crystal nucleating agent to a propylene homopolymer or a propylene random copolymer may be used for the outer layer. The crystal nucleating agent here is an additive (transparent nucleating agent) used to increase the transparency by controlling the size of the crystal component in the resin to be small. The amount of the crystal nucleating agent is preferably 1.0 part by weight or less with respect to 100 parts by weight of the polymer, more preferably more than 0 part by weight and 1.0 part by weight or less, and 0.05 to 0 More preferably, it is 5 parts by weight. If the amount of the crystal nucleating agent exceeds the upper limit, the effect of promoting the formation of crystal nuclei will reach its peak, and the manufacturing cost will simply increase.

  The crystal nucleating agent is not particularly limited, and those commonly used in the field may be used, but nonitol crystal nucleating agent, sorbitol crystal nucleating agent, phosphate ester crystal nucleating agent, triaminobenzene derivative crystal It is preferably selected from nucleating agents, carboxylic acid metal salt-based crystal nucleating agents, and organic nucleating agents such as xylitol-based crystal nucleating agents and rosin-based crystal nucleating agents. Examples of the nonitol crystal nucleating agent include 1,2,3-trideoxy-4,6: 5,7-bis-[(4-propylphenyl) methylene] -nonitol. Examples of the sorbitol-based crystal nucleating agent include 1,3: 2,4-bis-o- (3,4-dimethylbenzylidene) -D-sorbitol. Examples of the phosphate ester crystal nucleating agent include phosphoric acid-2,2'-methylenebis (4,6-di-tert-butylphenyl) lithium salt crystal nucleating agent. Examples of the triaminobenzene derivative-based crystal nucleating agent include 1,3,5-tris (2,2-dimethylpropanamide) benzene. Examples of the carboxylic acid metal salt-based crystal nucleating agent include sodium adipate, potassium adipate, aluminum adipate, sodium sebacate, potassium sebacate, aluminum sebacate, sodium benzoate, aluminum benzoate, di-para-t -Aluminum butyl benzoate, titanium di-para-t-butyl benzoate, chromium di-para-t-butyl benzoate, aluminum hydroxy-di-t-butyl benzoate and the like. Examples of the xylitol-based crystal nucleating agent include bis-1,3: 2,4- (5 ′, 6 ′, 7 ′, 8′-tetrahydro-2-naphthaldehydebenzylidene) 1-allylxylitol, bis-1,3. : 2,4- (3 ′, 4′-dimethylbenzylidene) 1-propylxylitol. Rosin-based crystal nucleating agents include rosin acids such as pimaric acid, sandaracopimalic acid, parastrinic acid, isopimaric acid, abietic acid, dehydroabietic acid, neoabietic acid, dihydropimaric acid, dihydroabietic acid, tetrahydroabietic acid, calcium, A rosin acid metal salt compound or a rosin acid partial metal salt compound obtained by a reaction with a metal such as magnesium, for example, a rosin acid partial calcium salt. The said crystal nucleating agent may be used individually by 1 type, and may use 2 or more types together.

  In addition to the above, the polymer constituting the outer layer includes antioxidants, chlorine absorbers, heat stabilizers, light stabilizers, UV absorbers, internal lubricants, external lubricants, antiblocking agents, antistatic agents, antifogging agents. Usually used in olefin polymers such as additives, flame retardants, dispersants, copper damage inhibitors, neutralizers, plasticizers, foaming agents, foam inhibitors, crosslinkers, peroxides, oil-extended and other organic and inorganic pigments Conventional additives used may be added. The addition amount of each additive may be a known amount.

  When adding a crystal nucleating agent and other additives to the polymer constituting the outer layer, after stirring the polymer, crystal nucleating agent, and other additives obtained by polymerization with a Henschel mixer, Brabender, etc. The composition can be obtained by melt blending at 180 ° C. to 280 ° C. using an extruder, and this can be used as a material for the outer layer. The addition of the crystal nucleating agent and other additives may be performed using a connected extruder after polymerization, residual monomer removal, and a drying step. Further, a so-called master batch obtained by melt-kneading a high concentration crystal nucleating agent with polyolefin may be mixed in a molding process of a polyolefin multilayer sheet or the like.

  Moreover, the polymer which comprises an outer layer may contain 1 type or multiple types of resin or rubbers other than polyolefin resin in the range which does not impair the effect of this invention. The content may be a known amount.

(2) Core layer Although a core layer may be comprised by arbitrary polyolefin, it is preferable that the polypropylene composition containing a component (1) and a component (2) is included. Component (1) is a propylene homopolymer, a propylene copolymer, or a blend of a propylene homopolymer and a propylene copolymer. Component (2) is an ethylene copolymer. The weight ratio of component (1) to component (2) is 60 to 90:40 to 10, preferably 65 to 85:35 to 15. If the amount of the component (2) exceeds the upper limit, the rigidity of the sheet or the like decreases, and if it is less than the lower limit, the cold shock resistance of the sheet or the like decreases.

(2-1) Component (1)
Component (1) is a propylene homopolymer, a propylene copolymer, or a blend of a propylene homopolymer and a propylene copolymer. These can be in any weight ratio, but preferably propylene copolymer containing as component (1) a propylene homopolymer and a comonomer selected from the group consisting of ethylene and C4-C10-α-olefins. The blend is a blend with a weight ratio of 10 to 97:90 to 3 and a comonomer content in the blend of 3% by weight or less. That is, in the component (1), the content of the propylene homopolymer is 10 to 97% by weight. If the content is less than the lower limit, the rigidity is lowered, and if it exceeds the upper limit, molding conditions for improving the balance of transparency, cold shock resistance, and rigidity are limited. In this respect, the content of the propylene homopolymer is preferably 40 to 90% by weight. The propylene copolymer is preferably a propylene random copolymer.

  The comonomer content in the blend is 3% by weight or less. When the content exceeds the upper limit value, the rigidity decreases. From this viewpoint, the comonomer content is preferably 1.8% by weight or less. As one aspect, the propylene homopolymer and the propylene copolymer having a comonomer content of 0.2 to 10% by weight are appropriately blended in the range of 40 to 95:60 to 5 (weight ratio), Propylene homopolymer content and comonomer content can be achieved. From the viewpoint of industrially inexpensive and stable distribution and easy availability, ethylene is preferable as the comonomer.

(2-2) Component (2)
Component (2) is an ethylene copolymer composed of a copolymer of ethylene and one or more C3-C10-α-olefins. The ethylene content is 60 to 90% by weight, preferably 65 to 85% by weight. When the ethylene content exceeds the upper limit, the cold shock resistance of the obtained sheet or the like is lowered, and when it is less than the lower limit, the transparency of the sheet or the like is lowered. The α-olefin is a C3 to C10 α-olefin, and propylene or butene-1 is preferable from the viewpoint of industrially inexpensive and stable distribution and relatively easy availability.

(2-3) Additive The polypropylene composition may contain a crystal nucleating agent of 1.0 part by weight or less, preferably 0.3 part by weight or less, but not 100 parts by weight of the composition. It is more preferable. If the amount of the crystal nucleating agent exceeds the upper limit value, the effect of promoting the formation of crystal nuclei will reach its peak, and the production cost will simply increase.

  In addition to this, polyolefins constituting the core layer include antioxidants, chlorine absorbers, heat stabilizers, light stabilizers, ultraviolet absorbers, internal lubricants, external lubricants, antiblocking agents, antistatic agents, antifogging agents. Usually used in olefin polymers such as additives, flame retardants, dispersants, copper damage inhibitors, neutralizers, plasticizers, foaming agents, foam inhibitors, crosslinkers, peroxides, oil-extended and other organic and inorganic pigments Conventional additives used may be added. The addition amount of each additive may be a known amount.

  When adding a crystal nucleating agent and other additives to the polyolefin constituting the core layer, after stirring the polymer, crystal nucleating agent, and other additives obtained by polymerization with a Henschel mixer, Brabender, etc. The composition can be obtained by melt blending at 180 ° C. to 280 ° C. using an extruder, and this can be used as the material for the core layer. The addition of the crystal nucleating agent and other additives may be performed using a connected extruder after polymerization, residual monomer removal, and a drying step. Further, a so-called master batch obtained by melt-kneading a high concentration crystal nucleating agent with polyolefin may be mixed in a molding process of a polyolefin multilayer sheet or the like.

(2-4) Characteristics [MFR]
The polypropylene composition preferably has an MFR of 1.0 to 10 g / 10 min. The MFR is measured at 230 ° C. and a load of 2.16 kg. If the MFR exceeds the upper limit value, it becomes difficult to draw down at the time of molding, so that it is difficult to produce a sheet or the like.

[XSIV]
The polypropylene composition preferably has an XSIV of 0.5 to 2.0 dl / g. XSIV is the intrinsic viscosity of the xylene soluble matter at 25 ° C. of the polypropylene composition. The xylene-soluble component is a component having no crystallinity, and XSIV is an index of the molecular weight of the component. The main component of xylene solubles is derived from component (2). XSIV in the composition is obtained by obtaining a component soluble in xylene at 25 ° C. and measuring the intrinsic viscosity of the component by a conventional method. When XSIV exceeds the upper limit, the transparency of the obtained sheet or the like is lowered, and when it is less than the lower limit, the production stability of the polypropylene composition is lowered.

[Phase structure]
The polypropylene composition preferably has a phase structure in which the component (2) is dispersed in the component (1). Whether the matrix component (1) is a blend of a propylene homopolymer and a propylene copolymer can be confirmed by DSC. For example, it can be confirmed by performing DSC analysis according to the method described in paragraph 0037 of JP2011-184686A. Specifically, the melting curve by thermal analysis when the polypropylene composition used in the present invention is reheated after repeating heating and cooling a plurality of times so that the maximum heating temperature sequentially decreases satisfies the following x to z. In this case, component (1) is a blend of a propylene homopolymer and a propylene copolymer.
x) The melting peak temperature is 165 ° C. or higher.
y) The proportion of components that melt at 170 ° C. or higher is 5% or higher.
z) The proportion of components that melt at 160 ° C. or lower is 15% or higher.

  The polypropylene composition may contain one or more resins or rubbers other than the polyolefin resin as long as the effects of the present invention are not impaired. The content may be a known amount.

(2-5) Method for Producing Polypropylene Composition As described above, propylene homopolymer or propylene copolymer can be used alone as component (1), but a propylene homopolymer and a propylene copolymer are blended. It can also be used. For convenience, the propylene homopolymer of component (1) is referred to as “component (1h)”, and the propylene copolymer is referred to as “component (1c)”. The polypropylene composition comprising component (1h), component (1c), and component (2) can be produced by any method. For example, it can be produced by the following method.

  Method 1: A method of preparing and mixing polymers of each component. For example, a method comprising polymerizing raw material monomers of component (1h), component (1c) and component (2) to produce respective polymers, and mixing the three.

  Method 2: A method of preparing and mixing the blend of component (1) and the polymer of component (2). For example, the raw material monomer of the other component is polymerized in the presence of either the polymer of component (1h) or component (1c) to obtain the other polymer, or the raw materials of components (1h) and (1c) A method comprising polymerizing monomers and mixing them while producing each component polymer to obtain a blend of component (1), and mixing the blend with the polymer of component (2).

  Method 3: A step of polymerizing the raw material monomer of component (2) in the presence of the polymer of component (1h) to prepare a blend, a step of polymerizing the raw material monomer of component (1c) to obtain a polymer, and Mixing the blend and the polymer.

Method 4: A method comprising polymerizing the raw material monomer of component (2) in the presence of the polymer of component (1c). For example, the following method is mentioned.
Method 4-1: a step of polymerizing the raw material monomer of component (2) in the presence of the polymer of component (1c) to prepare a blend, a step of polymerizing the raw material monomer of component (1h) to obtain a polymer, And mixing the blend and polymer.
Method 4-2: A step of polymerizing the raw material monomer of component (2) in the presence of the polymer of component (1c) to obtain blend 1, and the raw material of component (2) in the presence of the polymer of component (1h) A method comprising polymerizing monomers to obtain blend 2 and mixing both.

  Method 5: A method in which the raw material monomer of component (2) is polymerized in the presence of a blend of component (1). For example, a method comprising preparing a blend of component (1) and blending the three components while polymerizing the raw material monomers of component (2) in the presence of the blend.

  Among these, as described later, the method 4 or 5 is preferable from the viewpoint of dispersibility of the component (1c) and the component (2) containing a specific amount of the comonomer. In particular, it is preferable to polymerize the raw material monomer of the component (2) in the presence of the polymer of the component (1c) as in the method 4 because a sheet having excellent transparency in low temperature molding can be obtained. In general, it is often difficult to produce a polypropylene composition having a relatively large amount of component (2). However, in the presence of component (1h) as in method 3 or method 4-2, component (2) When the raw material monomer is polymerized, there is an advantage that the amount of the component (2) can be adjusted without making the production difficult, and the balance between rigidity and impact resistance can be easily obtained when a sheet or the like is formed. The mixing method of the polymer or the blend is not limited, but it is preferable to prepare powders or pellets of each component and mix them using a known mixer or extruder. The method for producing a blend in methods 2 to 5 and the like can be performed using, for example, a reactor having two or more reactors or two or more polymerization regions. The catalyst used for the polymerization is not limited and a known product may be used. The blend produced by such a method is called a so-called polymerization blend. Details of the polymerization method will be described later.

(3) Intermediate layer The intermediate layer may contain any polymer as long as the effects of the present invention are not impaired. For example, a return material obtained by recycling a sheet having three layers according to the present invention can be used for the intermediate layer.

(4) Properties of polyolefin multilayer sheet and the like The polyolefin multilayer sheet and the like of the present invention have various excellent effects due to this because the outer layer can be made extremely thin. For example, a three-layer sheet in which polypropylene containing 0 to 5.0% by weight of a comonomer selected from the group consisting of ethylene and C4 to C10-α-olefin is an outer layer, and the polypropylene composition is a core layer is taken as an example. I will explain. Since the sheet has a core layer having a phase structure in which the component (2) is dispersed in the component (1), the cold shock resistance of the sheet is improved, but the external haze is increased. On the other hand, the outer layer has a small external haze due to the absence of irregularities on the surface because there are no components with greatly different melting points. That is, the core layer contributes to cold shock resistance such as a sheet, and the outer layer contributes to improvement of transparency. When the outer layer is thick, the cold shock resistance is lowered. However, in the present invention, the outer layer is extremely thin, so the cold shock resistance is not lowered. From the above, the polyolefin multilayer sheet exhibits excellent transparency and cold shock resistance.

1. Preparation of polymer (1) Polymer for outer layer [Polymer A1]
The solid catalyst used for the polymerization was prepared by the method described in Example 1 of EP 6749991. The solid catalyst is obtained by supporting Ti and diisobutyl phthalate as an internal donor on MgCl ₂ by the method described in the above patent publication. The solid catalyst, triethylaluminum (TEAL) and cyclohexylmethyldimethoxysilane (CHMMS) are added in an amount such that the weight ratio of TEAL to the solid catalyst is 8 and the weight ratio of TEAL / CHMMS is 6.5. For 5 minutes. The resulting catalyst system was prepolymerized by keeping it in suspension in liquid propylene at 20 ° C. for 5 minutes.
After the obtained prepolymer was introduced into the polymerization reactor, hydrogen and propylene were fed, the polymerization temperature and the hydrogen concentration were adjusted to 75 ° C. and 0.113 mol%, respectively, and the pressure was adjusted so that A coalescence was produced. 0.5 parts by weight of Millad NX8000J (Nonitol, manufactured by Milliken Co.) as a crystal nucleating agent is added to 100 parts by weight of the polymer powder, and 0.2 parts by weight of BA225 B225 as an antioxidant is a neutralizing agent. As a result, 0.05 part by weight of calcium stearate manufactured by Tamnan Chemical Co., Ltd. was added, and the mixture was stirred for 1 minute with a Henschel mixer and mixed. This mixture was extruded at a cylinder temperature of 230 ° C. using an NVC φ50 mm single screw extruder manufactured by Nakatani Machinery Co., Ltd., and the strand was cooled in water, then cut with a pelletizer to obtain a pellet-shaped propylene resin composition, and a polymer. A1. The polymer A1 is a polypropylene composition containing a crystal nucleating agent. The Tm of the polymer was 166 ° C.

[Polymer A2]
Diisopropyldimethoxysilane (DIPMS) is used in place of cyclohexylmethyldimethoxysilane (CHMMS), TEAL / DIPMS weight ratio is 3.2, ethylene is fed in addition to hydrogen and propylene, polymerization temperature is 75 ° C, hydrogen concentration A propylene-ethylene copolymer was produced in the same manner as in the case of the polymer A1, except that 0.12 mol% and the ethylene concentration were 0.45 mol%. Heavy weight was obtained in the same manner as in Polymer A1, except that 0.25 parts by weight of Millad 3988 (sorbitol-based, manufactured by Milliken Corporation) was added as a crystal nucleating agent to 100 parts by weight of the obtained polymer powder instead of Millad NX8000J. Combined A2 was obtained. Polymer A2 is a polypropylene composition containing a crystal nucleating agent. The Tm of the polymer was 153 ° C.

(2) Resin composition for core layer [Polymer B1]
A solid catalyst in which Ti and diisobutyl phthalate as an internal donor were supported on MgCl ₂ was prepared by the method described in Example 5 of European Patent No. 728769. Then, using the above solid catalyst, TEAL as the organoaluminum compound, and dicyclopentyldimethoxysilane (DCPMS) as the external electron donor compound, the weight ratio of TEAL to the solid catalyst is 20, and the weight ratio of TEAL / DCPMS is 10. Such contact was made at 12 ° C. for 24 minutes. The resulting catalyst system was prepolymerized by keeping it in suspension in liquid propylene at 20 ° C. for 5 minutes. The obtained prepolymer is introduced into a first polymerization reactor of a polymerization apparatus equipped with a two-stage polymerization reactor in series, propylene is fed, and a propylene homopolymer is produced in a propylene liquid phase state. In the second stage gas phase polymerization reactor, an ethylene / butene-1 copolymer was produced. During the polymerization, temperature and pressure were adjusted, and hydrogen was used as a molecular weight modifier.
The polymerization temperature and the ratio of the reactants are as follows: in the first-stage reactor, the polymerization temperature and hydrogen concentration are 70 ° C. and 0.05 mol%, respectively, and in the second-stage reactor, the polymerization temperature, H2 / C2, C4 / (C2 + C4) were 80 ° C., 0.22 molar ratio, and 0.52 molar ratio, respectively. Further, the residence time distributions in the first and second stages were adjusted so that the amount of the copolymer component was 30% by weight. Polymer A1 except that Adeka Stub NA-71 (phosphate ester, manufactured by ADEKA Corporation) was added as a crystal nucleating agent to 100 parts by weight of the obtained polymer powder instead of Millad NX8000J. In the same manner as above, a polymer B1 was obtained. Polymer B1 is a polypropylene composition in which an ethylene-butene-1 copolymer is dispersed in a propylene homopolymer matrix and contains a crystal nucleating agent.
Table 1 summarizes the properties of the polymer.

2. Production of polyolefin multilayer sheet Using a T-die extruder (Soken Co., Ltd.) equipped with two types of three-layer feed blocks, a three-layer sheet (particularly referred to as “multilayer sheet before secondary processing”) is produced from the polymer. Evaluation was made by the method described below.
The T die was a 300 mm coat hanger die, and the lip width was 1.5 mm. The screw configuration was as follows.
For core layer: Full flight screw (φ30mm, L / D = 38, CR 2.75)
For outer layer: Full flight screw (φ25mm, L / D = 25, CR 3.2)
The multilayer sheet before secondary processing obtained above is heated at 150 ° C. or 160 ° C. for 120 seconds, biaxially stretched using a Bruckner film stretcher (KARO), and the total thickness is 0.2-0. A 4 mm three-layer sheet (in particular, also referred to as “sheet-like laminate” or “sheet-like laminate after secondary processing”) was obtained. The biaxial stretching was performed assuming secondary processing such as vacuum forming, pressure forming, and vacuum / pressure forming. The conditions and evaluation results are summarized in Table 2.

3. Analysis and Evaluation (1) Polymer or the ethylene content of each component in the polymer About a sample dissolved in a 1,2,4-trichlorobenzene / deuterated benzene mixed solvent, JNM LA-400 (manufactured by JEOL Ltd.) ¹³ C resonance frequency 100 MHz) and calculated from the value measured by ¹³ C-NMR method.
(2) MFR
According to JIS K 7210-1, the measurement was performed under conditions of a temperature of 230 ° C. and a load of 2.16 kg.
(3) XSIV
2.5 g of sample was placed in a flask containing 250 ml of o-xylene (solvent) and stirred for 30 minutes at 135 ° C. while purging with nitrogen using a hot plate and a reflux apparatus to completely dissolve the sample. . The solution was then cooled at 25 ° C. for 1 hour. Filter the resulting solution using filter paper, collect 100 ml of the filtrate, transfer to an aluminum cup, etc., evaporate to dryness at 150 ° C. while purging with nitrogen, and allow to stand at room temperature for 30 minutes to dissolve xylene. Got the minute. Using an Ubbelohde viscometer, the intrinsic viscosity was measured in 135 ° C. tetrahydronaphthalene of the xylene solubles to obtain XSIV (dl / g).

(4) Tm of polymer
The Tm of the polymer was measured by performing a second scan as defined above using a Perkin Elmer diamond DSC.

(5) Cold impact resistance A multilayer sheet before secondary processing was used as a test specimen for measurement. Using a hydroshot HITS-P10 manufactured by Shimadzu Corporation, a test specimen for measurement was placed on a support with a hole with an inner diameter of 40 mmφ and fixed using a sample presser with an inner diameter of 76 mmφ in a tank adjusted to −30 ° C. Thereafter, a test piece was hit with an impact speed of 1 m / sec with a striker having a diameter of 12.7 mmφ having a hemispherical hitting surface, and puncture energy (J) was determined according to JIS K7211-2. The average value of the puncture energy of each of the four test specimens for measurement was defined as the surface impact strength.

(6) Transparency A multilayer sheet before secondary processing and a sheet-like laminate after secondary processing obtained as described above using HM-150 manufactured by Murakami Color Research Laboratory Co., Ltd. according to ISO 14782 The haze measurement was performed using the test piece as a test piece, and the transparency was evaluated. In order to exclude the influence of surface irregularities, liquid paraffin (Liquid Paraffin Cat. No. 32033-00) was applied to both sides of the test piece with a brush, and haze measurement was performed in the same manner. The former was defined as “all haze” and the latter as “internal haze”. In order to see the contribution of the surface, “external haze” (“total haze” − “internal haze”) was defined.

(7) Thickness Regarding the multilayer sheet before secondary processing, equally divided in the width direction into 5 equal parts, each central part was cut into 3 cm x 3 cm to make a test piece, and the average value obtained by measuring with a thickness gauge The total thickness. Furthermore, after cutting the cross section of the test piece with a microtome, the outer layers on both the front and back surfaces were observed with a polarizing microscope with a magnification of 100 times, and the thicknesses of the outer layers on both the front and back surfaces of the micrograph were measured with calipers. Converted to actual thickness. The average value of the measured values of 10 thickness gauges on the front and back surfaces of the five test pieces was taken as the thickness of the outer layer. In addition, the standard deviation of the thickness of the outer layer was obtained from 10 points of measurement. Regarding the post-secondary sheet-like laminate used for the transparency evaluation, the average value obtained by measuring the transparency measurement position with a thickness gauge is the total thickness, and the outer layer of the post-secondary sheet-like laminate is obtained. The thickness was determined from the following.
(Total thickness of sheet-like laminate after secondary processing) × (thickness of outer layer of multilayer sheet before secondary processing) / (total thickness of multilayer sheet before secondary processing)

In Examples 1 to 6 shown in Table 2, even when the outer layer was thin, it was uniform, and a polyolefin multilayer sheet having a balance between cold shock resistance and transparency could be formed. On the other hand, in Comparative Example 1, the variation in the thickness of the outer layer in the width direction of the sheet was large, and the obtained sheet exhibited a poor appearance as gloss unevenness as a whole, and the external haze was large and the transparency was deteriorated. Furthermore, the rotation speed of the outer layer cylinder was set to be more than 8 rpm and less than 30 rpm, but the gloss unevenness and deterioration of the external haze of the multilayer sheet before the secondary processing were not solved. In Comparative Example 2, the gloss unevenness and the external haze of the multilayer sheet before the secondary processing were eliminated, but the outer layer was thick and the cold shock resistance was deteriorated. In Comparative Example 3, the sheet could not be formed due to the torque increase of the extruder.
It is clear that the polyolefin multilayer sheet obtained by the production method of the present invention has an excellent balance between cold shock resistance and transparency.

1 Raw material resin inlet 2 Feed zone 3 Compression zone 4 Weighing zone

Claims (10)

A polyolefin multilayer sheet or film comprising an outer layer and a core layer and satisfying the following i) and ii):
i) The thickness of the outer layer is 1/40 to 1/100 of the total thickness, and is 2 to 50 μm. ii) The core layer is a manufacturing method that is thicker than the outer layer,
Coextruding the outer layer and the core layer to form a polyolefin multilayer sheet or film satisfying i) and ii),
An extruder for forming the outer layer in the co-extrusion step includes a feed zone and a compression zone from upstream,
The temperature T (° C.) of the feed zone satisfies the relationship of the formula (1).
Tm−50 ° C. ≦ T ≦ Tm−10 ° C. (1)
(Tm is the melting point (° C) of the raw material polyolefin)
Production method. The polyolefin multilayer sheet or film obtained by the coextrusion step further includes a step of secondary processing so as to satisfy the above i) and ii).
The manufacturing method according to claim 1.   The manufacturing method of Claim 1 or 2 in which the said outer layer contains the polypropylene containing 0 to 5.0 weight% of comonomer selected from the group which consists of ethylene and C4-C10-alpha-olefin. The polypropylene composition wherein the core layer is:
Component (1) is a blend of a propylene homopolymer and a propylene copolymer containing a comonomer selected from the group consisting of ethylene and C4 to C10-α-olefin, the weight ratio of the two being 10 to 97 : 90 to 3 and the comonomer content in the blend is 3% by weight or less, and as component (2), 60 to 90% by weight of ethylene and one or more C3-C10-α-olefins An ethylene copolymer consisting of a copolymer with
The following (i) to (iii) are provided: (i) The weight ratio of the component (1): component (2) is 60 to 90:40 to 10
(Ii) MFR (230 ° C., load 2.16 kg) is 1.0 to 10 g / 10 min. (Iii) XSIV (xylene soluble intrinsic viscosity) is 0.5 to 2.0 dl / g,
The manufacturing method in any one of Claims 1-3 containing these.   The manufacturing method of Claim 4 with which the said multilayer sheet or film is provided with the layer of 3 or more layers, and the said outer layer is located in both outermost surfaces.   The manufacturing method according to claim 5, wherein the multilayer sheet or film has a three-layer structure.   The manufacturing method according to any one of claims 1 to 6, wherein the polypropylene composition has a phase structure in which the component (2) is dispersed in the component (1). The comonomer in component (1) is ethylene;
The manufacturing method in any one of Claims 4-7 whose (alpha) -olefin in the said component (2) is a propylene or butene-1.   The manufacturing method in any one of Claims 3-8 whose comonomer in the said polypropylene is ethylene.   The multilayer sheet or film obtained by the manufacturing method in any one of Claims 1-9.

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