Resin laminate

Abstract

To provide a resin laminate which has thin film thickness suitable for forming a complicated shape due to thermoforming such as vacuum forming, pressure forming and vacuum pressure forming, and has little deviation in draw down and molding.SOLUTION: A resin laminate has an unstretched layer (A) and a stretched layer (B) stacked directly or through other layer on both sides or one side of the unstretched layer (A), and has a thickness of 300-600 μm, wherein the unstretched layer (A) has no hole, and contains a polyolefin-based resin (A-1) having a rate of strain hardening (λmax(1.0)) in measurement of elongation viscosity at a rate of strain of 1.0 s-1 of 6.0 or more and has a branch structure, and polypropylene (A-2) having the rate of strain hardening (λmax(1.0)) of less than 6.0, the stretched layer (B) contains 50 mass% or more of polypropylene (B-1), provided that the polypropylene (A-2) and the polypropylene (B-1) may be the same or different.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin laminate. [Background technology]

[0002] Polypropylene resin sheets are easy to mold and have low raw material costs, resulting in low production costs. Their low density also makes them easy to handle and reduces transportation costs. Therefore, they are widely used for thermoforming to produce various containers, trays, and the like.

[0003] Patent Document 1 discloses a polypropylene resin for extrusion foaming in which drawdown during molding is prevented by adjusting the relationship between the melt tension (MT) and the melt flow rate (MFR).

[0004] Furthermore, Patent Document 2 discloses a thermoforming sheet that contains a polypropylene resin having specific properties, a thermoplastic elastomer, and a filler, and that has little sagging during molding, good formability to a mold, and can produce a molded product with little thickness deviation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-80262 [Patent Document 2] Japanese Patent Application Publication No. 2017-71767 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Documents 1 and 2, sheets having a thickness of 1 mm or more are used, particularly to suppress thickness variations. However, thermoforming using such thick sheets makes it difficult to accurately form minute and complex shapes, such as trays used for separating, storing, and transporting small items such as cosmetics, or even smaller items such as electronic components.

[0007] Furthermore, the sheet described in Patent Document 1 is a foamed sheet, and thermoformed articles formed using the foamed sheet tend to have insufficient mechanical strength and durability, and are poor in processability for forming complex and fine shapes.

[0008] The present invention relates to a resin laminate having a thin thickness suitable for molding into complex shapes by thermoforming such as vacuum molding, pressure molding, and vacuum-pressure molding, and which has little drawdown or thickness deviation during molding. [Means for solving the problem]

[0009] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, it was found that by forming a resin laminate in which an unstretched layer (A) and a stretched layer (B) containing a specific resin are laminated together, it is possible to obtain a resin laminate having a thin film thickness suitable for molding into a complex shape by thermoforming such as vacuum molding, pressure molding, and vacuum pressure molding, and which has little drawdown or thickness deviation during molding, and thus the present invention was completed. That is, the present invention is as follows.

[0010] [1] A resin laminate having a thickness of 300 to 600 μm, comprising: an unstretched layer (A); and an oriented layer (B) laminated on either or both sides of the unstretched layer (A) directly or via another layer; The non-stretched layer (A) is non-porous and stretched at a strain rate of 1.0 s -1 The composition comprises a polyolefin resin (A-1) having a branched structure and a strain hardening coefficient (λmax(1.0)) of 6.0 or more as measured by extensional viscosity at 1000 K, and a polypropylene (A-2) having the strain hardening coefficient (λmax(1.0)) of less than 6.0, the stretched layer (B) contains 50% by mass or more of polypropylene (B-1), In the resin laminate, the polypropylene (A-2) and the polypropylene (B-1) may be the same or different. [2] The resin laminate according to [1], wherein the polypropylene (A-2) has a melt flow rate of 5.0 g / 10 min or less. [3] The resin laminate according to [1] or [2], wherein the content of the polyolefin resin (A-1) relative to the total amount of the polypropylene (A-2) and the polyolefin resin (A-1) is 10 to 50 mass %. [4] The resin laminate according to any one of [1] to [3], which has an antistatic layer (C) on the outermost surface of either one or both surfaces. [5] The resin laminate according to [4], wherein the antistatic layer (C) is a coating layer containing an antistatic agent. [6] The resin laminate according to [5], wherein the antistatic agent comprises a cationic polymer antistatic agent. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a resin laminate having an unstretched layer and a stretched layer, which has a thin film thickness suitable for molding into a complex shape by thermoforming such as vacuum molding, pressure molding, and vacuum-pressure molding, and which has little drawdown or thickness deviation during molding. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is an overall view schematically showing a tray molded for measuring thickness deviation in the examples. [Figure 2] FIG. 2 is a bottom view of a tray for schematically showing the measurement points of thickness deviation in the examples. [Figure 3] FIG. 3 is a diagram schematically showing a cross section taken along line XX in FIG. [Figure 4]FIG. 4 is a side view of a tray for schematically showing the measurement points of the thickness deviation amount in the example. DETAILED DESCRIPTION OF THE INVENTION

[0013] The resin laminate of the present invention will be described in detail below. The following is an example (typical example) of the present invention, and the present invention is not limited thereto. In this specification, the numerical range "A to B" indicates "A or more and B or less."

[0014] The present invention provides a resin laminate having a thickness of 300 to 600 μm, which comprises an unstretched layer (A) and an oriented layer (B) laminated on either or both sides of the unstretched layer (A) directly or via another layer, wherein the unstretched layer (A) is non-porous and can be stretched at a strain rate of 1.0 s -1 and polypropylene (A-2) having a strain hardening coefficient (λmax(1.0)) of less than 6.0, wherein the stretched layer (B) contains 50 mass % or more of polypropylene (B-1), and the polypropylene (A-2) and the polypropylene (B-1) may be the same or different. By forming a resin laminate in which an unstretched layer (A) containing a specific resin and an oriented layer (B) are laminated together, it is possible to obtain a resin laminate that has a thin film thickness suitable for molding into complex shapes by thermoforming such as vacuum molding, pressure molding, and vacuum pressure molding, and that has little drawdown or thickness deviation during molding.

[0015] [Resin laminate] The thickness of the resin laminate is 300 to 600 μm, preferably 400 to 500 μm. By making the resin laminate have a thickness in this range, it is possible to accurately form complex shapes such as trays and containers that can be used to separate, store, and transport small items such as cosmetics, or even smaller items such as electronic components. If the thickness of the resin laminate is less than 300 μm, the molding window during vacuum molding may be narrow, resulting in poor productivity, and the vacuum molded product may be weak and difficult to handle.If the thickness of the resin laminate is more than 600 μm, the heating time during vacuum molding may increase, resulting in poor productivity, and the product may not conform to the mold well, resulting in poor molding.

[0016] Generally, when a thermoformed sheet is made thinner, it tends to have uneven thickness and be more susceptible to drawdown. However, the resin laminate of the present invention has an unstretched layer (A) and an oriented layer (B) laminated on either or both sides of the unstretched layer (A) directly or via another layer, and therefore has good thermoformability even when it is thin.

[0017] [Non-stretched layer (A)] The non-stretched layer (A) was non-porous and stretched at a strain rate of 1.0 s -1 The composition contains a polyolefin resin (A-1) having a branched structure and a strain hardening coefficient (λmax(1.0)) of 6.0 or more as measured by extensional viscosity at 1000 K, and a polypropylene (A-2) having the strain hardening coefficient (λmax(1.0)) of less than 6.0.

[0018] The non-oriented layer (A) is non-porous, which provides the following advantages over thermoforming sheets that use a foam as a layer corresponding to the non-oriented layer (A) (for example, thermoforming sheets described in JP-A Nos. 11-80262 and 8-318602): The thermoformed product obtained has high mechanical strength and excellent durability. -Compared to thermoforming sheets of the same thickness, it is possible to form deep-draw molded bodies with more complex shapes. -When heating before molding, heat is easily transferred to the inside of the base material, allowing for consistent production of high-quality molded products and excellent productivity.

[0019] In this specification, "non-porous" means that the porosity is 5% or less. Here, "porosity" means the ratio (volume ratio) of the volume occupied by pores in a target layer to the total volume of the target layer. The porosity can be obtained as the area ratio of pores on the cross section, calculated by observing the cross section of the target layer with a scanning electron microscope, importing the observed image into an image analyzer, and performing image analysis on the observed region.

[0020] The melt tension of the unstretched layer (A) is preferably 30 to 250 mN, more preferably 35 to 200 mN. A melt tension of 30 mN or more is preferable because it reduces the amount of drawdown during thermoforming of a resin laminate containing the unstretched layer. A melt tension of 250 mN or less is also preferable because it makes the molten resin sheet less likely to tear during sheet molding and facilitates molding.

[0021] The non-oriented layer (A) may be a single layer or a multilayer.

[0022] The thickness of the unstretched layer (A) is preferably 200 to 595 μm, more preferably 300 to 495 μm. A thickness of 200 μm or more is preferable because thickness deviation is less likely to occur and a molded product of good quality is easily obtained. Furthermore, a thickness of 595 μm or less is preferable because a deep-draw molded product of a more complex shape can be formed and the molding time can be shortened.

[0023] (Polyolefin resin (A-1)) The unstretched layer (A) was stretched at a strain rate of 1.0 s -1 The composition contains a polyolefin resin (A-1) having a branched structure and a strain hardening coefficient (λmax(1.0)) of 6.0 or more as measured by extensional viscosity at 1000 K.

[0024] Here, the strain hardening coefficient (λmax(1.0)) is an index representing the strength when melted, and a larger value of this coefficient has the effect of improving the melt tension. As a result, even when molding a molded article with a complex shape, it is possible to prevent the defect phenomenon of excessive thickness deviation from being formed during thermoforming, and this contributes to improving the physical properties of the molded article and also to reducing the thickness of the raw sheet (gauge down), making it possible to suitably mold various containers, trays, etc. If the strain hardening coefficient of the polyolefin resin (A-1) is less than 6.0, thickness deviation may occur during thermoforming, and moldability may be reduced. The strain hardening coefficient of the polyolefin resin (A-1) is preferably 8.0 or more, more preferably 12.0 or more, and from the viewpoint of shapeability during thermoforming, the strain hardening coefficient is further preferably 17.0 or less.

[0025] Strain rate 1.0 s -1 The method for calculating the strain hardening rate λmax (1.0) in the measurement of the extensional viscosity at 1000 kJ / s is described below. Temperature: 180°C, strain rate: 1.0 s -1 The extensional viscosity in this case is plotted on a double logarithmic graph with time t (seconds) on the horizontal axis and extensional viscosity ηE (Pa·seconds) on the vertical axis. On the double logarithmic graph, the relationship between time and viscosity up to just before strain hardening occurs is approximated by a straight line to obtain an approximation line. Specifically, first, the slope at each time point when the extensional viscosity is plotted against time is determined, and in doing so, various averaging methods are used, taking into account that the extensional viscosity measurement data is discrete. For example, one method is to determine the slope of each adjacent data point and take the moving average of several surrounding points. In the low strain range, the extensional viscosity is a simple increasing function, gradually approaching a constant value. Without strain hardening, it coincides with the Trouton viscosity after a sufficient time has passed. However, with strain hardening, the extensional viscosity generally begins to increase with time from a strain (= strain rate x time) of approximately 1. That is, the slope tends to decrease with time in the low strain range, but begins to increase from a strain of approximately 1. When the extensional viscosity is plotted against time, an inflection point is present on the curve. Therefore, the point where the slope at each time calculated above is at its minimum value in the strain range of approximately 0.1 to 2.5 is determined, a tangent is drawn at that point, and a straight line is extrapolated until the strain reaches 4.0. The maximum value (ηmax) of the extensional viscosity ηE until the strain reaches 4.0 and the time at which this maximum value is reached are determined, and the viscosity on the approximate straight line at that time is defined as ηlin. ηmax / ηlin is defined as λmax(1.0).

[0026] Examples of the polyolefin resin (A-1) include polyethylene or polypropylene having a long-chain branched structure.

[0027] The melt tension of the polyolefin resin (A-1) is preferably from 75 to 600 mN, more preferably from 100 to 500 mN. A melt tension of 75 mN or more is preferable because it can impart the desired melt tension to the resin laminate and easily improve drawdown. A melt tension of 600 mN or less is also preferable because it improves compatibility with the polypropylene (A-2) described below. If the melt tension is too high, the sheet may be easily torn during sheet molding, making sheet molding difficult. The melt tension was measured at a take-up speed of 10 mm / min at 190°C.

[0028] The melt flow rate of the polyolefin resin (A-1) is preferably from 0.5 to 10 g / 10 min, and more preferably from 1.0 to 8.0 g / 10 min. A melt flow rate of 0.5 g / 10 min or more is preferable because it improves sheet formability, and a melt flow rate of 10 g / 10 min or less is preferable because it suppresses necking during sheet forming and makes it easier to obtain a sheet of uniform thickness. The melt flow rate in this specification refers to a value measured by an appropriate method depending on the type of monomer component that is most abundant in the resin. For example, in the case of propylene, the value measured at 230°C under a load of 2.16 kg in accordance with JIS K7210 was used, and in the case of polyethylene, the value measured at 190°C under a load of 2.16 kg in accordance with JIS K6922-2 was used.

[0029] (Polypropylene (A-2)) The unstretched layer (A) was stretched at a strain rate of 1.0 s -1 The polypropylene (A-2) has a strain hardening coefficient (λmax(1.0)) of less than 6.0 as measured by elongational viscosity at 1000 K.

[0030] The polypropylene (A-2) may be any of a propylene homopolymer, a random polypropylene, and a block polypropylene, or these may be used in combination. As the propylene homopolymer, polypropylenes showing isotactic or syndiotactic and various stereoregularities may be used.

[0031] The polypropylene (A-2) is preferably a resin with a low melt flow rate, since this increases the melt tension and can suppress drawdown during thermoforming. The melt flow rate of the polypropylene (A-2) is preferably 5.0 g / 10 min or less, more preferably 3.0 g / 10 min or less, and even more preferably 2.0 g / 10 min or less.

[0032] (Content of polypropylene (A-2) and polyolefin resin (A-1)) The total amount of polypropylene (A-2) and polyolefin resin (A-1) in the non-stretched layer (A) is preferably 70 mass% or more based on the total mass of all components constituting the non-stretched layer (A), and more preferably 100 mass% when the non-stretched layer (A) does not contain the inorganic filler (A-3) described below. When the total amount of the polypropylene (A-2) and the polyolefin resin (A-1) is 70% by mass or more, the excellent thermoformability, which is an effect of the present invention, is fully exhibited, and this is therefore preferred.

[0033] The content of the polyolefin resin (A-1) relative to the total amount of the polypropylene (A-2) and the polyolefin resin (A-1) is preferably from 10 to 50% by mass, more preferably from 20 to 40% by mass. By setting the content of the polyolefin resin (A-1) to 10% by mass or more relative to the total amount of the polypropylene (A-2) and the polyolefin resin (A-1), a decrease in strain hardening of the resin composition, a decrease in moldability due to the occurrence of thickness deviation, and an increase in the amount of drawdown tend to be suppressed, which is preferable. Also, by setting the content to 50% by mass or less, an excessive increase in melt tension is suppressed, which tends to reduce the possibility that the raw sheet is easily torn during sheet molding and the possibility that the sheet breaks due to an excessively high strain hardening during vacuum molding, which is preferable.

[0034] (Inorganic filler (A-3)) The non-stretched layer (A) may contain an inorganic filler (A-3). The inclusion of the inorganic filler (A-3) is preferred because it improves the mechanical strength of the molded article. Examples of the inorganic filler (A-3) include inorganic fine powders such as calcium carbonate, calcined clay, silica, diatomaceous earth, talc, titanium oxide, barium sulfate, and alumina. The average primary particle size of the inorganic fine powder is preferably 0.01 to 15 μm. It is preferable that the inorganic fine powder has an average primary particle size of 0.01 μm or more, since this prevents the generation of secondary coarse particles due to aggregation of the inorganic fine powder during melt extrusion. Also, it is preferable that the inorganic fine powder has an average primary particle size of 15 μm or less, since this prevents the inorganic fine powder from protruding from the sheet surface and thus prevents defects from appearing on the outermost surface. The average primary particle size (D50) is measured by a laser light diffraction / scattering method using, for example, a Microtrac MT3300EXII (manufactured by Microtrac Bell).

[0035] When the non-stretched layer (A) contains an inorganic filler (A-3), the content of the inorganic filler relative to the total mass of all components constituting the non-stretched layer (A) is preferably 15 to 30 mass%, more preferably 18 to 27 mass%. By containing the inorganic filler (A-3) in the non-stretched layer (A), the amount of resin contained in the molded article is reduced, which is preferable from the viewpoint of reducing the environmental load caused by resins. The content of inorganic filler (A-3) is preferably 15% by mass or more, since this improves the mechanical strength of the molded article. Furthermore, the content of inorganic filler (A-3) is preferably 30% by mass or less, since this suppresses an increase in the amount of drawdown due to an increase in specific gravity and also prevents a decrease in moldability due to an excessively low relative resin content. When the non-stretched layer (A) contains inorganic filler (A-3), the total amount of polypropylene (A-2) and polyolefin resin (A-1) contained in the layer is preferably 70 to 85% by mass, more preferably 73 to 82% by mass.

[0036] (Other optional ingredients) The unstretched layer (A) may further contain, as necessary, a stabilizer, a light stabilizer, a dispersant, a lubricant, etc. For example, 0.001 to 1 mass % of a sterically hindered phenol-based, phosphorus-based, amine-based, or other stabilizer may be blended as the stabilizer, 0.001 to 1 mass % of a sterically hindered amine, benzotriazole-based, benzophenone-based, or other light stabilizer may be blended as the light stabilizer, and 0.01 to 4 mass % of a silane coupling agent, a higher fatty acid such as oleic acid or stearic acid, or a metal soap may be blended as a dispersant for the inorganic filler.

[0037] The non-oriented layer (A) may contain a polyolefin resin other than the polyolefin resin (A-1) and the polypropylene (A-2), or another thermoplastic resin, as long as the effects of the present invention are not impaired.

[0038] [Stretched layer (B)] The stretched layer (B) contains 50% by mass or more of polypropylene (B-1).

[0039] By laminating the stretched layer (B) directly or via another layer on both sides or one side of the unstretched layer (A), drawdown can be suppressed. More specifically, the stretched layer (B) on the surface shrinks due to heat during thermoforming using the resin laminate, thereby suppressing drawdown of the unstretched layer (A).

[0040] The stretched layer (B) may be a single layer or a multilayer.

[0041] The thickness of the stretched layer (B) is preferably 20 to 100 μm, more preferably 40 to 80 μm. A thickness of 20 μm or more of the stretched layer (B) is preferred because excessive shrinkage of the stretched layer during heating in thermoforming can be suppressed. Furthermore, a thickness of 100 μm or less of the stretched layer (B) is preferred because uneven heating of the unstretched layer (A) during thermoforming can be reduced.

[0042] The stretched layer (B) may be laminated on only one side of the unstretched layer (A) or on both sides thereof. When laminated on both sides, the two stretched layers (B) may be the same or different. From the viewpoint of production costs, it is preferable that the stretched layer (B) is laminated on only one side of the unstretched layer (A), and from the viewpoint of suppressing curling of the laminate, it is preferable that the stretched layer (B) is laminated on both sides of the unstretched layer (A).

[0043] The oriented layer (B) may be a uniaxially oriented layer, a biaxially oriented layer, or a combination thereof. By forming the stretched layer (B) as a biaxially stretched layer, shrinkage of the stretched layer (B) due to heat during thermoforming using the resin laminate occurs in biaxial directions, which further suppresses drawdown, and is therefore preferred.

[0044] When the stretched layer (B) has a multilayer structure, the number of stretching axes of each layer may be the same or different. By combining layers with different numbers of stretching axes, it is possible to design a stretched layer (B) that has both the advantages of uniaxial stretching and biaxial stretching. The number of stretching axes of each layer may be, for example, uniaxial / uniaxial, uniaxial / biaxial, biaxial / uniaxial, uniaxial / uniaxial / biaxial, uniaxial / biaxial / uniaxial, biaxial / uniaxial / uniaxial, uniaxial / biaxial / biaxial, biaxial / biaxial / uniaxial, or biaxial / biaxial / biaxial / uniaxial.

[0045] When the stretched layer (B) is laminated on both sides or one side of the unstretched layer (A) via another layer, examples of the other layer include other unstretched layers described below in [Other layers].

[0046] (Polypropylene (B-1)) The stretched layer (B) contains 50% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more of polypropylene (B-1). There is no particular upper limit to the content of polypropylene (B-1) in the stretched layer (B), and it may be 100% by mass. When the content of polypropylene (B-1) in the stretched layer (B) is less than 50% by mass, if the remainder is mostly an organic filler and / or an inorganic filler described below, breakage during sheet molding or molding defects in the vacuum molded product may occur. If the remainder is mostly other resins, this is not preferable from the viewpoint of recyclability of the molded product.

[0047] The polypropylene (B-1) may be the same as or different from the polypropylene (A-2).

[0048] Examples of the polypropylene (B-1) include the same resins as those exemplified as the polypropylene (A-2). When the polypropylene (B-1) is the same as the polypropylene (A-2), the stretched layer (B) contains, as a main component, the same polypropylene as the unstretched layer (A). This improves the recyclability of the resin laminate and molded articles produced using the same, and is preferable because it makes it easy to adjust the melt viscosities of the resin compositions constituting the unstretched layer (A) and the stretched layer (B) to be approximately the same during shaping, making it easy to stably obtain molded articles.

[0049] When the polypropylene (B-1) is different from the polypropylene (A-2), the polypropylene (B-1) may be, for example, a resin that differs from the polypropylene (A-2) in the type of monomer copolymerized with propylene, copolymerization ratio, molecular weight, etc.

[0050] The melt flow rate of the polypropylene (B-1) is preferably from 0.5 to 15 g / 10 min, more preferably from 3.0 to 10 g / 10 min, and even more preferably from 3.0 to 8.0 g / 10 min. A melt flow rate of 0.5 g / 10 min or more is preferable because it improves sheet formability, and a melt flow rate of 15 g / 10 min or less is preferable because it increases the melt tension of the resin composition forming the stretched layer (B) and makes it easier to ensure thermoformability such as vacuum forming.

[0051] (other thermoplastic resins) The stretched layer (B) may contain a thermoplastic resin other than polypropylene (B-1) to the extent that the effects of the present invention are not impaired. Examples of such thermoplastic resins include ethylene-based resins such as high-density polyethylene and medium-density polyethylene, polyolefin-based resins such as propylene-based resins that are copolymers of propylene with α-olefins such as ethylene, butene-1, hexene-1, and heptene-1,4-methylpentene-1, polymethyl-1-pentene, ethylene-cyclic olefin copolymers, polyamide-based resins such as nylon-6, nylon-6,6, nylon-6,10, and nylon-6,12, thermoplastic polyester-based resins such as polyethylene terephthalate and its copolymers, polyethylene naphthalate, and aliphatic polyesters, polycarbonate, atactic polystyrene, syndiotactic polystyrene, and polyphenylene sulfide. These may also be used in combination. Among these, propylene-based resins and high-density polyethylene are preferably selected from the viewpoints of cost, water resistance, and chemical resistance.

[0052] (Other optional ingredients) The stretched layer (B) may further contain an inorganic filler and / or an organic filler, if necessary.

[0053] Examples of inorganic fillers that may be contained in the stretched layer (B) include the same examples as those of the inorganic filler (A-3) listed as an optional component of the non-stretched layer (A). When both the non-stretched layer (A) and the stretched layer (B) contain inorganic fillers, the inorganic filler contained in the stretched layer (B) may be the same as or different from that contained in the non-stretched layer (A).

[0054] The organic filler that may be contained in the stretched layer (B) may be an organic fine powder having a melting point or glass transition temperature higher than the melting point of the polypropylene (B-1) contained in the stretched layer (B) and the melting points of the other thermoplastic resins described above. When the main component of the stretched layer (B) is an olefin-based resin, examples of the organic fine powder that can be used include polyethylene terephthalate, polybutylene terephthalate, polycarbonate, nylon-6, nylon-6,6, homopolymers of cyclic olefins, copolymers of cyclic olefins and ethylene, and the like, which have a melting point of 120 to 300°C or a glass transition temperature of 120 to 280°C.

[0055] The content of inorganic filler and / or organic filler in the stretched layer (B) is preferably 0.5 to 60% by mass, more preferably 3 to 50% by mass. A content of inorganic filler and / or organic filler of 0.5% by mass or more is preferred because it improves moldability. Furthermore, a content of 60% by mass or less is preferred because it makes the stretched layer (B) less likely to break during stretching.

[0056] The stretched layer (B) may further contain, as necessary, a stabilizer, a light stabilizer, an ultraviolet absorber, a dispersant, a lubricant, etc. For example, 0.001 to 1 mass % of a sterically hindered phenol-based, phosphorus-based, amine-based, or other stabilizer may be blended as the stabilizer, 0.001 to 1 mass % of a sterically hindered amine, benzotriazole-based, benzophenone-based, or other light stabilizer may be blended as the light stabilizer, and 0.01 to 4 mass % of a silane coupling agent, a higher fatty acid such as oleic acid or stearic acid, or a metal soap may be blended as a dispersant for inorganic fine powder.

[0057] [Lamination method of non-stretched layer (A) and stretched layer (B)] There are various methods for laminating the stretched layer (B) integrally to one or both surfaces of the unstretched layer (A), but for example, the following methods (a) to (c) are preferred. (a) A thermal lamination method in which the resin composition for the non-oriented layer (A) is melted and kneaded in an extruder, and then extruded from a co-extrusion die. While the resin composition is still in a molten state, the heat is used to pressurize and weld the oriented layer (B) onto one side of the extruded layer using a metal or rubber roll. (a) A method in which the unstretched layer (A) and the stretched layer (B) are bonded together with a hot melt adhesive or a solvent adhesive. (c) In the case of (a), a known adhesive hot-melt adhesive layer is provided on the unstretched layer (A) by co-extrusion, or a stretched layer (B) provided with a hot-melt adhesive layer is used.

[0058] As will be described later, when the non-stretched layer (A) has another non-stretched layer on one or both sides thereof, the non-stretched layer (A) and the stretched layer (B) may be indirectly laminated together to produce the resin laminate of the present invention by replacing the "non-stretched layer (A)" in the above explanations (a) to (c) with "non-stretched sheet (A)" including the non-stretched layer (A) and the other non-stretched layer.

[0059] (adhesion) Examples of hot melt adhesives used to bond the oriented layer (B) integrally to one or both sides of the unoriented layer (A) include low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer (preferably an ethylene-vinyl acetate copolymer having a vinyl acetate content of 12% by mass or less), ethylene-acrylic acid copolymer (preferably an ethylene-acrylic acid copolymer having an ethylene content of 65 to 94% by mass), ethylene-methacrylic acid alkyl ester copolymer, ionomer (metal salt of ethylene-acrylic acid copolymer or metal salt of ethylene-methacrylic acid copolymer), ethylene-propylene copolymer, ethylene-propylene-butene-1 copolymer, vinyl chloride-vinyl acetate copolymer, etc. Two or more of these may be used in combination.

[0060] Examples of solvent-based adhesives include polyether polyol-polyisocyanate adhesives and polyester polyol-polyisocyanate adhesives. Two or more of these may be used in combination. The thickness of such adhesive layers is generally 1 to 30 μm, preferably 1 to 20 μm. Specifically, coating-type adhesives are used in a thickness of 1 to 20 g / m. 2 , preferably 2 to 8 g / m 2 The hot melt adhesive is melt-extrusion laminated and heat-sealed to a thickness of 6 to 30 μm, preferably 8 to 20 μm.

[0061] [Antistatic layer (C)] The resin laminate may have an antistatic layer (C) on both sides or on one side as the outermost layer. The antistatic layer (C) may be provided on either the surface of the oriented layer (B) or the surface of the unoriented layer (A), provided that it is the outermost layer of the resin laminate.

[0062] When the molded article is a container or tray, friction with the articles stored therein may cause the molded article itself or the stored articles to become charged. To prevent this, it is preferable to use an antistatic agent in the moldable resin laminate. In the field of resin molding, kneaded-in antistatic agents are widely used, but kneading an antistatic agent into a resin composition for layer formation can sometimes cause a decrease in the viscosity of the resin composition. Therefore, from the viewpoint of drawdown resistance, it is preferable to form an antistatic layer containing an antistatic agent on the outermost surface of a resin laminate, rather than using a kneaded-in antistatic agent. That is, it is preferable that the antistatic agent be contained in the resin laminate by providing an antistatic layer containing the antistatic agent, preferably a coating layer containing the antistatic agent provided by coating.

[0063] Furthermore, when molded products are crushed, melted, and kneaded for reuse in molding, resin compositions containing antistatic agents are prone to resin degradation due to re-melting and kneading. Generally, in the case of kneaded-in antistatic agents, a larger amount of antistatic agent is required to achieve the desired antistatic properties than when an antistatic layer is applied by coating, increasing the risk of resin degradation during reuse. On the other hand, when an antistatic layer is applied to the surface of a resin laminate by coating, a high antistatic effect is achieved with a smaller amount and a thinner layer, making resin degradation less likely during reuse and preferable from the standpoint of recyclability.

[0064] The thickness of the antistatic layer (C) is preferably 0.001 to 10 μm, more preferably 0.005 to 0.1 μm. By making the thickness of the antistatic layer (C) 0.001 μm or more, the desired antistatic properties can be obtained, which is preferable. Furthermore, by making the thickness of the antistatic layer (C) 10 μm or less, the recyclability of the final product is excellent and there is a cost advantage, which is preferable.

[0065] (antistatic agent) The antistatic agent contained in the antistatic layer (C) is preferably one that does not bleed out from the surface of the resin laminate during thermoforming and does not pose a risk of contaminating articles that come into contact with the resulting molded article. Even in the case of an antistatic layer provided by coating, an antistatic agent that does not migrate to the surface of an article that comes into contact with it when the molded article is obtained is desired. Therefore, it is preferable that the antistatic agent be one that can be applied to form a layer by coating using water, which has a low environmental impact, as a solvent or dispersion medium, and that does not migrate to the surface of the molded product during thermoforming.

[0066] As such an antistatic agent, a polymer type antistatic agent is preferred. Examples of the polymer type antistatic agent include cationic, anionic, amphoteric, and nonionic antistatic agents. These can be used alone or in combination of two or more.

[0067] Examples of cationic antistatic agents include antistatic agents having an ammonium salt structure, a phosphonium salt structure, etc. Examples of anionic antistatic agents include antistatic agents having an alkali metal salt structure (lithium salt, sodium salt, potassium salt, etc.) of sulfonic acid, phosphoric acid, carboxylic acid, etc. The anionic antistatic agent may be an antistatic agent having an alkali metal salt structure of acrylic acid, methacrylic acid, maleic acid (anhydride), etc. in its molecular structure.

[0068] Examples of amphoteric antistatic agents include antistatic agents containing both cationic and anionic antistatic agent structures in the same molecule. Examples of amphoteric antistatic agents include betaine antistatic agents. Examples of nonionic antistatic agents include ethylene oxide polymers having an alkylene oxide structure and polymers having an ethylene oxide polymerization component in the molecular chain. Other examples of antistatic agents include polymer antistatic agents having boron in the molecular structure.

[0069] Among these, as the polymer-type antistatic agent, a cationic polymer-type antistatic agent is preferred, a nitrogen-containing polymer-type antistatic agent is more preferred, a polymer-type antistatic agent having an ammonium salt structure is even more preferred, an acrylic resin having a tertiary or quaternary ammonium salt structure is particularly preferred, and an acrylic resin having a quaternary ammonium salt structure is most preferred. As the cationic polymer antistatic agent, commercially available products such as Saftomer ST-1000, ST-1100, and ST-3200 (trade names) manufactured by Mitsubishi Chemical Corporation can be used.

[0070] (Method for forming antistatic layer (C)) The method for forming the antistatic layer (C) is not particularly limited. For example, a coating liquid is prepared by dispersing or dissolving the components of the antistatic layer in water, and the print-receiving layer can be formed by applying the coating liquid to a substrate and drying it. For coating, a known coating device such as an air knife coater, gravure coater, blade coater, roll coater, reverse roll coater, bar coater, curtain coater, die slot coater, champlex coater, size press coater, gate roll coater, or bill blade coater can be used.

[0071] [Other layers] The resin laminate of the present invention may have layers other than the non-stretched layer (A), the stretched layer (B), and the antistatic layer (C) described above, provided that the effects of the present invention are not impaired. For example, the surface of the non-stretched layer (A) may have another non-stretched layer that does not contain the polyolefin resin (A-1). In this case, the stretched layer (B) or the antistatic layer (C) may be laminated to the non-stretched layer (A) via the other non-stretched layer, and the other non-stretched layer may also function as an adhesive layer.

[0072] The resin contained in the other unstretched layer is not particularly limited as long as it is a thermoplastic resin, and examples thereof include polyolefin-based resins, polyamide-based resins, and polyester-based resins. However, polyolefin-based resins are preferred because they can be formed by co-extrusion with the unstretched layer (A) without the use of adhesives. Specific examples include ethylene-based resins such as high-density polyethylene and medium-density polyethylene, as well as the polypropylenes listed above as examples of polypropylene (A-2), and propylene-based resins that contain propylene as the main component and are copolymers of this with α-olefins such as ethylene, butene-1, hexene-1, and heptene-1,4-methylpentene-1. Furthermore, various known additives may be contained as necessary. The other non-oriented layer may be provided on both sides of the non-oriented layer (A) or on only one side.

[0073] [Applications of resin laminates] The resin laminate of the present invention can be suitably used as a thermoforming sheet for producing, for example, various containers, trays, and the like. [Example]

[0074] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to the following examples.

[0075] [Raw materials] In the examples and comparative examples, the raw materials used for the unstretched layer (A) are as shown in Table 1.

[0076] [Table 1]

[0077] The melt flow rate, melt tension, and strain hardening of each raw material were measured by the following methods.

[0078] (Melt Flow Rate) Polypropylene was measured at 230°C under a load of 2.16 kg in accordance with JIS K7210, and polyethylene was measured at 190°C under a load of 2.16 kg in accordance with JIS K6922-2.

[0079] (melt tension) Measurements were taken using a Capilograph 1D manufactured by Toyo Seiki Seisakusho Co., Ltd., at a test temperature of 190°C, using a capillary with a length of 20 mm and a diameter of 2.0 mm, and a take-up speed of 10 mm / min.

[0080] (Strain hardening degree) Uniaxial extensional viscosity was measured using a TA Instruments ARES-G2 in uniaxial extensional mode at 180°C under N2 with a sample size of 20 mm length and 10 mm width. Melt viscosity was measured using the same instrument in shear mode at 180°C under N2 with a parallel plate of 25 mm diameter. Then, the temperature was 180°C and the strain rate was 1.0 s -1The extensional viscosity in this case was plotted on a double logarithmic graph with time t (seconds) on the horizontal axis and extensional viscosity ηE (Pa·seconds) on the vertical axis. The relationship between time and viscosity just before strain hardening occurred on the double logarithmic graph was obtained using an approximation line. The maximum value (ηmax) of extensional viscosity ηE when the strain amount reached 4.0 and the time at which this maximum value was reached were determined, and the viscosity on the approximation line at that time was taken as ηlin, with ηmax / ηlin being the degree of strain hardening (λmax(1.0)).

[0081] [Manufacturing Example 1] (Polymer-type antistatic agent) Into a four-neck flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube, 35 parts by mass of dimethylaminoethyl methacrylate, 20 parts by mass of ethyl methacrylate, 20 parts by mass of cyclohexyl methacrylate, 25 parts by mass of stearyl methacrylate, 150 parts by mass of ethyl alcohol, and 1 part by mass of 2,2'-azobisisobutyronitrile were added. After the system was purged with nitrogen, a polymerization reaction was carried out under a nitrogen stream at 80°C for 6 hours. Next, 70 parts by mass of a 60% by mass ethyl alcohol solution of 3-chloro-2-hydroxypropylammonium chloride was added, and the mixture was further reacted at a temperature of 80° C. for 15 hours. Next, ethyl alcohol was distilled off while ion-exchanged water was dropped into the reactor, to obtain an aqueous resin solution with a solids concentration of 30 mass% consisting of a methacrylic copolymer containing a quaternary ammonium salt group, which was used as a polymer-type antistatic agent (abbreviated as AS).

[0082] [Reference example] The polymer antistatic agent AS obtained in Production Example 1 and the low molecular weight antistatic agent ESR-381 (trade name: Rikemaster ESR-381, manufactured by Riken Vitamin Co., Ltd.; LDPE masterbatch containing 15 mass% of diglycerol monolaurate and N-dodecyl-N,N-diethanolamine monostearate, diglycerol monolaurate / N-dodecyl-N,N-diethanolamine monostearate (mass ratio) = 80 / 20, base resin: LDPE) were used to compare bleed-out properties during thermoforming by the following method.

[0083] (bleed-out properties) First, the polymer-type antistatic agent AS was diluted 50 times with water, and this was bar-coated onto the surface of a 100 μm-thick commercially available PET film using a No. 2 bar at a speed of 4 mm / min, followed by drying at 70°C for 2 minutes (test sheet 1).

[0084] The low molecular weight antistatic agent ESR-381 was pressed at 230°C and 15 MPa for 5 minutes, and then cooled while being pressed at 20°C and 15 MPa for 1.5 minutes to prepare a sheet with a thickness of 500 µm (test sheet 2).

[0085] The resulting test sheets 1 and 2 were each laminated with a commercially available transparent PET film having a thickness of 100 μm and pressed at 10 MPa at 130°C for 60 seconds. Test sheet 1 was laminated so that the surface coated with antistatic agent AS faced the transparent PET film. The transparent PET film was then peeled off, and the haze value of the transparent PET film with the antistatic agent transferred to its surface was measured using a Haze Meter NDH 2000 manufactured by Nippon Denshoku Industries Co., Ltd. The values ​​obtained by subtracting the haze value of the PET film itself from the measurement results are shown in Table 2. A larger value indicates a greater amount of bleed-out. Although test samples 1 and 2 have different thicknesses, the pressure conditions were the same, so this does not affect the evaluation results of bleed-out properties.

[0086] [Table 2]

[0087] Table 2 shows that polymer-type antistatic agent AS bleeds out less from molded products even under heat and pressure conditions than general low-molecular-weight antistatic agents.

[0088] [Example 1] (Production of stretched sheet B) (1) A resin composition (b1) was prepared by mixing 73.77 parts by weight of a propylene homopolymer (trade name "Novatec PP FY4" manufactured by Japan Polypropylene Corporation, melting point 164°C) with a melt flow rate (MFR (230°C)) of 5.0 g / 10 min, 10 parts by weight of a high-density polyethylene (trade name "Novatec HD HJ381" manufactured by Japan Polyethylene Corporation), 16 parts by weight of heavy calcium carbonate with an average particle size of 1.5 μm (trade name "Softon 1800" manufactured by Bihoku Funka Kogyo Co., Ltd.), and 0.23 parts by weight of an antioxidant (trade name "PEP-36" manufactured by ADEKA Corporation). The mixture was kneaded in an extruder set at 250°C, extruded into a sheet, and further cooled in a cooling device to obtain an unstretched sheet. The sheet was then reheated to a temperature of 150°C and stretched 5 times in the longitudinal direction to obtain a 5x longitudinally stretched resin film. (2) A resin composition (b2) obtained by mixing 51.77 parts by mass of a propylene homopolymer (trade name "Novatec PP FY4", manufactured by Japan Polypropylene Corporation, melting point 164°C) with MFR (230°C) of 5.0 g / 10 min, 3 parts by mass of a high-density polyethylene (trade name "Novatec HD HJ381", manufactured by Japan Polyethylene Corporation), 45 parts by mass of heavy calcium carbonate with an average particle size of 1.5 μm (trade name "Softon 1800", manufactured by Bihoku Funka Kogyo Co., Ltd.), and 0.23 parts by mass of an antioxidant (trade name "PEP-36", manufactured by ADEKA Corporation) was kneaded in another extruder set at 250°C, extruded into a sheet, and laminated on both sides of the 5x longitudinally stretched film obtained in the above step (1) to obtain a three-layer laminated film. (3) Next, this three-layer laminated film was cooled to a temperature of 60°C, heated again to a temperature of 155°C, stretched 9.0 times in the transverse direction using a tenter, annealed at a temperature of 165°C, and cooled to a temperature of 60°C. After that, the edge portions were slit to produce a three-layer structure (uniaxially stretched / biaxially stretched / uniaxially stretched) with a thickness of 70 μm (b2 / b1 / b2=13 μm / 44 μm / 13 μm) and a density (ρ) of 0.86 g / cm. 3 A stretched sheet B having an opacity of 84% and a whiteness of 96% was obtained, which was used as the stretched layer (B) in the present invention.

[0089] (Production of Unstretched Sheet A) an unstretched layer (A) containing 41.77 parts by mass of a propylene homopolymer having an MFR (230°C) of 5.0 g / 10 min (abbreviation: h-PP1, trade name "Novatec PP FY4", manufactured by Japan Polypropylene Corporation), 23 parts by mass of calcium carbonate having an average particle size of 1.25 μm (abbreviation: CaCO3, trade name "Softon 1800", manufactured by Bihoku Funka Kogyo Co., Ltd.), 25 parts by mass of a high-pressure low-density polyethylene having an MFR (190°C) of 0.5 g / 10 min (abbreviation: LDPE, trade name "Novatec LD LF129", manufactured by Japan Polyethylene Corporation), 10 parts by mass of a high-density polyethylene (abbreviation: HDPE, trade name "Novatec HD HJ381", manufactured by Japan Polyethylene Corporation), and 0.23 parts by mass of an antioxidant (abbreviation: antioxidant, trade name "PEP-36", manufactured by ADEKA Corporation); Another unstretched layer (a1) containing 66.77 parts by mass of propylene homopolymer h-PP1, 23 parts by mass of calcium carbonate CaCO3, 10 parts by mass of high-density polyethylene HDPE, and 0.23 parts by mass of an antioxidant; The unstretched layer (a2) was composed of 100 parts by mass of random polypropylene (propylene-ethylene random copolymer, product name: Novatec PP FW4B, manufactured by Japan Polypropylene Corporation). Each was melt-mixed at 220°C in a separate extruder, fed into a single die, laminated, and extruded to obtain a five-layer sheet with a structure of (a2) / (a1) / (A) / (a1) / (a2). The thickness of the unstretched sheet A was 370 μm, and the thicknesses of the individual layers were: unstretched layer (A): 240 μm, combined (a1): 120 μm, and combined (a2): 10 μm.

[0090] (Production of resin laminate) The stretched layer (B) was the aforementioned stretched sheet B, which was thermally laminated onto one side of the unstretched sheet A while the unstretched sheet A was still in a softened state, to obtain a resin laminate having a thickness of 440 μm.

[0091] The melt tension of the unstretched layer (A) was measured by the method described above.

[0092] [Examples 2 to 7] A resin laminate was produced in the same manner as in Example 1, except that the raw materials for the unstretched layer (A) were changed as shown in Table 3. Furthermore, in the same manner as in Example 1, the melt tension of the unstretched layer (A) was also measured.

[0093] [Comparative Example 1] Except for using h-PP1 instead of LDPE, a resin laminate was produced in the same manner as in Example 1. Furthermore, in the same manner as in Example 1, the melt tension of the non-oriented layer (A) was also measured.

[0094] Comparative Example 2 Only the unstretched sheet (A) was used without laminating the oriented layer (B). In addition, similarly to Example 1, the melt tension of the unstretched layer (A) was also measured.

[0095] (evaluation) The resin laminates obtained in the respective Examples and Comparative Examples were evaluated as follows.

[0096] (Measurement of drawdown amount) The obtained resin laminate was cut into a sample measuring 297 mm in length and 210 mm in width, and the drawdown amount was measured using a vacuum forming machine "FE36PH" manufactured by Sanwa Kogyo Co., Ltd. The measurement conditions were heater heating at 50% and heating for 35 seconds. The drawdown amount is preferably 50 mm or less.

[0097] (Measurement of thickness deviation) Using a small multi-function vacuum and compressed air molding machine "FKS-0632-20" manufactured by Asano Laboratories, a tray measuring 27.5 cm in length, 21.5 cm in width, and 2.0 cm in depth was vacuum molded, and the thickness of the molded product was measured using a thickness gauge manufactured by Olympus, PANAMETRICS-NDT Magna-Mike 8500. Figure 1 is a schematic overall view of the molded tray 1.

[0098] The thickness of tray 1 was measured at 25 locations on the bottom of the tray, 11 locations on the long sides, and 8 locations on the short sides, each at 4 cm intervals, as shown in Figures 2 to 4. Black circles in Figures 2 to 4 indicate the locations where the thickness was measured. Also, "..." in Figure 4 indicates that there were multiple thickness measurement locations (black circles) along the way. The thickness of the molded product was calculated by determining the difference between the maximum and minimum values ​​on the long side of the side, the difference between the maximum and minimum values ​​on the short side of the side, and the difference between the maximum and minimum values ​​on the bottom. The largest of the differences between the maximum and minimum values ​​calculated for the long side of the side, the short side of the side, and the bottom was determined as the thickness deviation.

[0099] [Table 3]

[0100] As is clear from Table 3, the resin laminates obtained in the Examples have a small amount of drawdown during thermoforming, are less likely to have thickness deviations, and are excellent in formability. On the other hand, the resin laminate obtained in Comparative Example 1 does not use the polyolefin resin (A-1) with high strain hardening, so it has a large amount of drawdown during molding, and is therefore inferior in formability. Comparative Example 2 does not have the stretched layer (B) laminated therein, so it has an even larger amount of drawdown, and is therefore even more inferior in formability. [Industrial Applicability]

[0101] The resin laminate of the present invention can be suitably used as a thermoforming sheet for producing, for example, various containers, trays, and the like. [Explanation of symbols]

[0102] 1 tray

Claims

1. A resin laminate having a thickness of 300 to 600 μm, comprising: an unstretched layer (A); and an oriented layer (B) laminated on either or both sides of the unstretched layer (A) directly or via another layer; The non-stretched layer (A) is non-porous and is stretched at a temperature of 180° C. at a strain rate of 1.0 s －１ The composition comprises a polyolefin resin (A-1) having a branched structure and a strain hardening coefficient (λmax(1.0)) of 6.0 or more as measured by extensional viscosity at 1000 K, and a polypropylene (A-2) having the strain hardening coefficient (λmax(1.0)) of less than 6.0, the total amount of the polypropylene (A-2) and the polyolefin resin (A-1) in the unstretched layer (A) is 70% by mass or more, the content of the polyolefin-based resin (A-1) relative to the total amount of the polypropylene (A-2) and the polyolefin-based resin (A-1) in the unstretched layer (A) is 10 to 50% by mass, the stretched layer (B) contains 50% by mass or more of polypropylene (B-1), However, the polypropylene (A-2) and the polypropylene (B-1) may be the same or different.

2. 2. The resin laminate according to claim 1, wherein the polypropylene (A-2) has a melt flow rate of 5.0 g / 10 min or less.

3. The resin laminate according to claim 1 or 2, which has an antistatic layer (C) on the outermost surface of either one or both surfaces.

4. The resin laminate according to claim 3 , wherein the antistatic layer (C) is a coating layer containing an antistatic agent.

5. The resin laminate according to claim 4 , wherein the antistatic agent comprises a cationic polymer antistatic agent.

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