Thermoplastic resin pellets, easily peelable adhesives, laminates, and container lid materials

Abstract

To provide thermoplastic resin pellets useful as a lid material for containers, sheets, and the like which comprise polyethylene as an adhesion surface.SOLUTION: Provided are thermoplastic resin pellets comprising a thermoplastic resin (E) and a thermoplastic resin (F) which is incompatible with the thermoplastic resin (E). In a cut surface formed when the pellet is cut parallel to a flow direction where the pellet was extruded from a dice, the thermoplastic resin (E) forms a matrix phase, the thermoplastic resin (F) is dispersed in the matrix phase to form a domain phase, an average major axis of the domain phase is in a range of 5 μm to 20 μm, and a ratio (major axis / minor axis) of the domain major axis and the domain minor axis is in a range of 3 to 15.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to thermoplastic resin pellets that are easily peelable from components such as containers that have polyethylene as their adhesion surface, an easily peelable adhesive, a laminate, and a lid material made thereof. [Background technology]

[0002] In recent years, there has been a clear trend towards placing greater importance on environmental adaptability and hygiene when it comes to food containers, and containers made from polyvinyl chloride, which emits harmful gases when burned, and polystyrene, which is suspected of having adverse health effects from leaching, are being replaced by containers made from polyethylene or polypropylene.

[0003] In particular, the use of polyethylene-laminated paper containers has increased significantly. Examples include yogurt containers, instant ramen containers, confectionery containers, etc., which are cup-shaped containers made by extrusion-laminating polyethylene onto paper.

[0004] The containers described above require lids that can be safely handled without breaking during transportation and that are easily peelable so that even women and children can open them.

[0005] Therefore, the above-mentioned easily peelable lid material has a layer (sealing layer) on the outermost layer that comes into contact with the polyethylene surface of the container and heat seals it, and an easily peelable adhesive having a specific composition is used for the sealing layer.

[0006] Examples of easily peelable adhesives include: 1) compositions in which a resin that is basically poorly adhesive to polyethylene (e.g., polypropylene) is mixed with a resin that can bond to polyethylene (e.g., polyethylene, ethylene-vinyl acetate copolymer, etc.); 2) so-called hot melt compositions in which an ethylene-vinyl acetate copolymer is mixed with a tackifier and a low molecular weight wax, etc.; 3) high molecular weight hot melt compositions that make the above hot melt types extrudable; 4) compositions in which low density polyethylene is blended with high molecular weight polybutene (see, for example, Patent Document 1); 5) easily peelable adhesives for polyethylene consisting of a polyethylene-based resin, a crystalline polybutene resin, and a low molecular weight wax (see, for example, Patent Document 2); and 6) easily peelable adhesives for polyethylene consisting of a polyethylene-based resin, a crystalline polypropylene-based resin, and a low molecular weight polyethylene wax (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 1-315443 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-129018 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-112955 Summary of the Invention [Problem to be solved by the invention]

[0008] However, when polyethylene resin and polypropylene or polybutene resin pellets are dry-blended, cracks in the molten film may occur during molding, or thickness accuracy may be poor, resulting in areas with low adhesive strength, resulting in poor peelability. On the other hand, when pellets obtained by pre-melting and kneading polyethylene resin and polypropylene or polybutene resin pellets are used, molding processability is improved, but so-called stringiness may occur frequently on the peeled surface upon opening, resulting in a poor peel appearance. For this reason, it has been difficult to achieve high opening strength while maintaining excellent molding processability and good opening appearance. [Means for solving the problem]

[0009] As a result of intensive research to solve the above problems, the inventors discovered that thermoplastic resin pellets having a certain phase structure have excellent molding processability, and when the sealing layer is made thin, they exhibit high opening strength, resulting in good sealing properties and an excellent appearance of the peel surface, which led to the present invention.

[0010] That is, the present invention relates to the following [1] to

[11] . [1] A thermoplastic resin pellet comprising a thermoplastic resin (E) and a thermoplastic resin (F) incompatible with the thermoplastic resin (E), wherein the thermoplastic resin pellet has a cut surface, when the pellet is cut parallel to the flow direction in which the pellet is extruded from a die, in which the thermoplastic resin (E) forms a matrix phase and the thermoplastic resin (F) is dispersed in the matrix phase to form a domain phase, and the domain phase has an average major axis in the range of 5 μm to 20 μm, and the ratio of the domain major axis to the domain minor axis (major axis / minor axis) is in the range of 3 to 15. [2] Thermoplastic resin pellets according to [1], characterized in that the thermoplastic resin (E) is a polyethylene-based resin, and the thermoplastic resin (F) is at least one selected from the group consisting of crystalline polybutene resin, crystalline polypropylene, crystalline ethylene-propylene copolymer, and crystalline ethylene-propylene-butene-1 copolymer. [3] Thermoplastic resin pellets according to [1] or [2], characterized in that they contain 60 to 90 parts by weight of thermoplastic resin (E) and 10 to 40 parts by weight of thermoplastic resin (F) (the total of (E) and (F) is 100 parts by weight). [4] An easily peelable adhesive comprising the thermoplastic resin pellets according to any one of [1] to [3]. [5] A method for producing thermoplastic resin pellets according to any one of [1] to [3], characterized in that the thermoplastic resin (E) and the thermoplastic resin (F) are mixed, melt-kneaded, and then produced using a pelletizing facility selected from the group consisting of an underwater cut facility, a strand cut facility, and a hot cut facility. [6] A laminate comprising a sealing layer (A), an intermediate layer (B), and a substrate (C) laminated in this order, wherein the sealing layer (A) is made of the easily peelable adhesive described in [4]. [7] The laminate according to [6], wherein the intermediate layer (B) is made of a polyethylene resin (D) having a melt mass-flow rate of 0.3 g / 10 min or more and less than 200 g / 10 min, the ratio of the thickness of the sealing layer (A) to the sum of the thicknesses of the sealing layer (A) and the intermediate layer (B) is 5% or more and less than 50%, and the thickness of the sealing layer (A) is 1 μm or more and less than 20 μm. [8] The laminate according to [6] or [7], wherein the polyethylene resin (D) constituting the intermediate layer (B) satisfies the following requirement (a): (a) The swell ratio (SR) calculated by dividing the diameter (D) of the strand extruded at a temperature of 235°C and an extrusion rate of 3 g / min using a melt indexer specified in JIS K 7210 by the orifice diameter (D0) of the melt indexer is 1.7 or more and 3.0 or less. [9] The laminate according to any one of [6] to [8], wherein the polyethylene resin (D) constituting the intermediate layer (B) is low-density polyethylene.

[10] The laminate according to any one of [6] to [9], wherein the polyethylene resin (D) constituting the intermediate layer (B) is an ethylene-α-olefin copolymer.

[11] A container lid material comprising the laminate according to any one of [6] to

[10] . [Effects of the Invention]

[0011] The thermoplastic resin pellets of the present invention have excellent moldability and processability, and in particular maintain excellent processability even when the sealing layer is made thin. They also have excellent sealing properties for adherends with polyethylene as their adhesive surface, and also have excellent appearance on the peeled surface. Therefore, they are useful as an easily peelable adhesive and as a packaging material for containers and the like whose adhesive surface is polyethylene, and are particularly ideal as a lid material for containers whose adhesive surface is polyethylene. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below.

[0013] A thermoplastic resin pellet according to one embodiment of the present invention is a thermoplastic resin pellet containing a thermoplastic resin (E) and a thermoplastic resin (F) that is incompatible with the thermoplastic resin (E), and when the pellet is cut parallel to the flow direction in which it is extruded from a die, the thermoplastic resin (E) forms a matrix phase, and the thermoplastic resin (F) is dispersed in the matrix phase to form domain phases, and the cut surface has an average major axis of the domain phase in the range of 5 μm or more and 20 μm or less, and the ratio of the domain major axis to the domain minor axis (major axis / minor axis) is in the range of 3 or more and 15 or less.

[0014] The thermoplastic resin (E) is not particularly limited, and examples thereof include polyethylene resins, polypropylene resins, ethylene-α-olefin copolymers, acid-modified versions of these olefin resins, ethylene-vinyl acetate copolymers, ethylene-α,β-unsaturated carboxylic acids, and esters thereof. Among these, polyethylene resins are preferred when the adherend is polyethylene, and polypropylene resins, ethylene-α-olefin copolymers, ethylene-vinyl acetate copolymers, ethylene-α,β-unsaturated carboxylic acids, and esters thereof are preferred when the adherend is polypropylene. In particular, when the adherend is polyethylene, low-density polyethylene is preferred among polyethylene resins in terms of extrusion lamination processability.

[0015] The melt mass flow rate of the thermoplastic resin (E) measured in accordance with JIS K6922-1 is not particularly limited, but is preferably 10 to 200 g / 10 min.

[0016] The thermoplastic resin (F) incompatible with the thermoplastic resin (E) is not particularly limited, and examples thereof include crystalline polybutene resin, crystalline polypropylene, crystalline ethylene-propylene copolymer, crystalline ethylene-propylene-butene-1 copolymer, and saponified ethylene-vinyl acetate copolymer. Among these, when the thermoplastic resin (E) is a polyethylene-based resin, crystalline polybutene resin, crystalline polypropylene, crystalline ethylene-propylene copolymer, and crystalline ethylene-propylene-butene-1 copolymer are preferred.

[0017] Furthermore, the thermoplastic resin (F) that is incompatible with the thermoplastic resin (E) preferably has a melting point of 150° C. or lower in terms of molding processability.

[0018] The melt mass flow rate of the thermoplastic resin (E) and the incompatible thermoplastic resin (F) measured in accordance with JIS K7210 is not particularly limited, but is preferably 1 to 30 g / 10 min, and particularly preferably 0.5 to 10 g / 10 min.

[0019] There are no particular restrictions on the blending ratio of the thermoplastic resin (E) and the incompatible thermoplastic resin (F), but a ratio of 60 to 90 parts by weight of the thermoplastic resin (E) to 10 to 40 parts by weight of the incompatible thermoplastic resin (F) (the total of (E) and (F) is 100 parts by weight) is preferred, as this results in good easy-open properties and good moldability.

[0020] A low-molecular-weight polyethylene wax (G) may be blended into the mixture of the thermoplastic resin (E) and the thermoplastic resin (F) incompatible with the thermoplastic resin (E). The low-molecular-weight polyethylene wax (G) preferably has a number-average molecular weight of 1,000 to 10,000 as determined by the GPC method.

[0021] The blending ratio of the low-molecular-weight polyethylene wax (G) is not particularly limited, but blending 3 to 20 parts by weight of the low-molecular-weight polyethylene wax (G) per 100 parts by weight of the total of the thermoplastic resin (E) and the incompatible thermoplastic resin (F) is preferred because it improves the molding processability and peeling appearance.

[0022] In the thermoplastic resin pellet of one embodiment of the present invention, when the pellet is cut, the thermoplastic resin (E) forms a matrix phase, the thermoplastic resin (F) is dispersed in the matrix phase to form a domain phase, and the domain phase has an average major axis in the range of 5 μm or more and 20 μm or less, and the ratio of the domain major axis to the domain minor axis (major axis / minor axis) is in the range of 3 or more and 15 or less on the cut surface.

[0023] The thermoplastic resin pellets have a so-called sea-island structure in which the thermoplastic resin (E) forms the sea portion (matrix) and the thermoplastic resin (F) forms the island portion (domain), and flat domains made of the thermoplastic resin (F) are dispersed.

[0024] In the present invention, the domain average major axis is the average major axis of elliptical domains that appear on a cross section when a thermoplastic resin pellet is cut near the center. The domain average major axis is in the range of 5 μm to 20 μm, and is preferably 6 μm to 15 μm, more preferably 6 μm to 12 μm, because this improves the opening strength and peel appearance.

[0025] In the present invention, the ratio of the domain major axis to the domain minor axis is determined by cutting the thermoplastic resin pellet near the center and measuring the length of the elliptical domain in the width direction perpendicular to the major axis from the major axis of the elliptical domain that appears on the cut surface. The ratio of the domain major axis to the domain minor axis (major axis / minor axis) is in the range of 3 to 15 μm, and is preferably 3 to 12, more preferably 3 to 10, in order to improve the peel appearance.

[0026] The thermoplastic resin pellets, which are one embodiment of the present invention, may be produced by any method, but are preferably produced by melt-kneading a mixture of thermoplastic resin (E) and thermoplastic resin (F) that is incompatible with thermoplastic resin (E) using granulation equipment such as underwater cutting equipment, strand cutting equipment, or hot cutting equipment.

[0027] The thermoplastic resin pellets are used as an easily peelable adhesive and as a sealing layer for a laminate.

[0028] The laminate according to one embodiment of the present invention comprises a seal layer (A), an intermediate layer (B), and a substrate (C) laminated in this order, with the seal layer (A) comprising the above-mentioned easily peelable adhesive.

[0029] The intermediate layer (B) is preferably made of a polyethylene resin (D) having an MFR of 0.3 g / 10 min or more and less than 200 g / 10 min, as measured in accordance with JIS K6922-1.

[0030] If the polyethylene resin (D) has an MFR of less than 0.3 g / 10 min, the extrusion load during extrusion lamination is large, resulting in poor processability and low tear strength when the laminate is heat-sealed and peeled off, which is undesirable.If the MFR is 200 g / 10 min or more, the melt tension during melting is insufficient, making stable molding difficult.

[0031] The polyethylene resin (D) is not particularly limited other than its MFR, and examples thereof include high-density polyethylene, linear polyethylene such as ethylene-α-olefin copolymer, low-density polyethylene, ethylene-vinyl acetate copolymer, and ethylene-unsaturated carboxylic acid copolymer. Low-density polyethylene or ethylene-α-olefin copolymer is particularly preferred. Among ethylene-α-olefin copolymers, copolymers of ethylene and an α-olefin having 3 to 8 carbon atoms are more preferred, and copolymers of ethylene and 1-butene are most preferred. Two or more of these resins may be mixed and used. Furthermore, two or more of the same resins with different physical properties such as MFR may be mixed and used.

[0032] Furthermore, the polyethylene resin (D) preferably has a swell ratio (SR) of 1.7 or more and 3.0 or less, more preferably 1.7 or more and 2.5 or less. When a resin having an SR in this range is used for the intermediate layer (B), the molding processability during extrusion lamination becomes good and further, when the laminate is heat-sealed and peeled, poor appearance such as stringiness at the peeled surface is reduced, which is preferable.

[0033] The SR can be measured by dividing the diameter (D) of a strand extruded at a temperature of 235°C and an extrusion rate of 3 g / min using a melt indexer as specified in JIS K 7210 by the orifice diameter (D0) of the melt indexer.

[0034] The sealing layer (A) and intermediate layer (B) constituting the laminate of the present invention may contain additives that are typically compounded in polyolefin resins, such as antioxidants, lubricants, antistatic agents, antifogging agents, and antiblocking agents, in the required amounts as long as they do not impair the performance of the laminate of the present invention.

[0035] In the laminate of the present invention, the ratio of the thickness of the sealing layer (A) to the sum of the thicknesses of the sealing layer (A) and the intermediate layer (B) is 5% or more and less than 50%, preferably 5% or more and 40% or less.

[0036] When the ratio of the thickness of the seal layer (A) to the sum of the thicknesses of the seal layer (A) and the intermediate layer (B) is 5% or more, the extrusion rates of the seal layer (A) and the intermediate layer (B) are well balanced when they are co-extrusion laminated, enabling stable molding processing. When the thickness ratio of the seal layer (A) is less than 50%, the distance over which the seal layer (A) breaks when the laminate is heat-sealed and peeled is not too long, and poor appearance upon peeling, such as stringiness, is unlikely to occur, which is undesirable.

[0037] There are no particular restrictions on the thickness of the sealing layer (A), but it is preferably 1 μm or more and less than 20 μm, more preferably 1 μm or more and 15 μm or less, to prevent peeling and other appearance defects such as stringiness.

[0038] The substrate (C) constituting the laminate according to one embodiment of the present invention is not particularly limited, and a material generally used as a substrate for a lid material can be used. Examples of the substrate (C) include stretched or unstretched films such as polyester film, polyamide film, and polypropylene film, and aluminum foil.

[0039] On the outside of the substrate (C), one or more layers of polyolefin film, polyester film, polyamide film, saponified ethylene-vinyl acetate copolymer film, paper, etc. may be further laminated.

[0040] The method for laminating the seal layer (A) and the intermediate layer (B) to the substrate (C) is not particularly limited, and examples thereof include a method in which the seal layer (A) and the intermediate layer (B) are each formed into a monolayer film by cast molding or inflation molding, and then sequentially laminated by dry lamination, a method in which the monolayer film-formed seal layer (A) and the substrate (C) are sandwich-laminated with the resin of the intermediate layer (B), a method in which the substrate (C) and the intermediate layer (B) are extrusion-laminated, and then the seal layer (A) is tandem-laminated, and a method in which the seal layer (A) and the intermediate layer (B) are coextrusion-laminated to the substrate (C). Among these, the method in which the seal layer (A) and the intermediate layer (B) are coextrusion-laminated to the substrate (C) is preferred because of the good adhesion between the layers and the economical advantage.

[0041] When laminating by extrusion lamination, the anchor coating agent may be applied in advance to a substrate such as a plastic film such as a polyester film or a polyamide film, or paper or aluminum foil. It is also preferable to perform ozone treatment during processing to laminate with various plastic films, aluminum foil, etc.

[0042] The laminate of the present invention can be used, for example, as a lid, more preferably as a lid for polyethylene containers. The object to which the laminate is adhered may be a container or sheet whose structure includes a packaging material with barrier properties, such as vinylidene chloride, ethylene-vinyl alcohol copolymer, or aluminum.

[0043] Examples of objects to which the laminate can be bonded include laminated containers obtained by boxing together a structure in which low-density polyethylene is laminated onto paperboard, and more specifically, paper cups for yogurt or instant ramen, etc. [Example]

[0044] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, the reagents used were commercially available products. The measurement methods used in the examples are shown below.

[0045] ~Melt Mass Flow Rate (MFR)~ The MFR of each material used was measured in accordance with JIS K6922-1.

[0046] ~Swell Ratio (SR)~ The SR of each material was measured using a melt indexer specified in JIS K 7210, where the diameter (D) of the extruded strand was divided by the orifice diameter (D0) of the melt indexer at a temperature of 235°C and an extrusion rate of 3 g / min.

[0047] Example 1 The thermoplastic resins constituting the seal layer (A) were low-density polyethylene (Petrothene 248, manufactured by Tosoh Corporation) with a MFR of 58 g / 10 min, and crystalline polypropylene (Novatec PP FW4BAT, manufactured by Japan Polypropylene Corporation, melting point 138 °C) with a MFR of 7 g / 10 min, in a blending ratio of 65 / 35 by weight. The mixture of thermoplastic resins (E) and (F) was melt-mixed in a twin-screw extruder (TEX25α-III, manufactured by The Japan Steel Works, Ltd.) using a weak mixing screw configuration with a single mixing zone, a processing temperature of 180 °C, and an extrusion rate of 20 kg / h. Then, thermoplastic resin pellets of the mixture were obtained using underwater cutting (UWC) equipment. When the resulting thermoplastic resin pellets were cut near the center parallel to the flow direction, the elliptical domains that appeared on the cut surface had an average major axis of 6 μm and a domain major axis / domain minor axis ratio (major axis / minor axis) of 4.

[0048] A film prepared by laminating a 12 μm thick polyester film (PET) and a 7 μm thick aluminum foil by dry lamination was used as the substrate (C). An isocyanate-based anchor coating agent (a 3 / 1 mixture of Takelac A-3210 and Takenate A-3072, manufactured by Mitsui Chemicals, Inc.) was applied to the aluminum foil side of the substrate (C). The intermediate layer (B) and the sealing layer (A) were then co-extrusion laminated using a 90 mm / 65 mm co-extrusion laminator at a processing speed of 120 m / min in the order substrate (C) / intermediate layer (B) / sealing layer (A), to obtain a laminate.

[0049] The middle layer (B) is a polyethylene resin (D) with a density of 924 kg / m 3 A composition was used (MFR: 17 g / 10 min, SR: 1.81) made by mixing a low-density polyethylene with a MFR of 45 g / 10 min (trade name: Petrothene 209, manufactured by Tosoh Corporation) and a low-density polyethylene with a density of 919 kg / m3 and a MFR of 1.6 g / 10 min (trade name: Petrothene 360, manufactured by Tosoh Corporation). The temperature inside the extruder cylinder was 340°C, and the layer thickness was 25 μm.

[0050] The resulting thermoplastic resin pellets were processed to form the sealing layer (A) under the conditions of an extruder cylinder temperature of 280°C, a die temperature of 335°C, and a layer thickness of 15 µm.

[0051] The obtained easily peelable resin pellets were visually inspected for film cracks to assess their moldability. The inspection results were evaluated as ◯ (no film cracks or holes) or × (film cracks or holes). The thickness of the laminate was also measured to confirm the thickness precision of the sealing layer. The inspection results were evaluated as ◯ (deviation of 2 μm or less), △ (greater than 2 and less than 5 μm), and × (5 μm or more). Furthermore, the width of the molten film of the laminate was measured to confirm the neck-in width. The inspection results were evaluated as ◯ (50 mm or less), △ (greater than 50 and less than 80 mm), and × (80 mm or more). In all cases, the evaluation results of ◯ and △ were judged to be good.

[0052] This laminate was used as a lid for the opening of a paper cup container (flange outer diameter 100 mm) with a 30 μm thick low-density polyethylene laminated on the inner surface, and heat-sealed so that the adhesive surfaces of the structure were in contact with each other using an overlap heat-sealing machine (manufactured by Sunny Pack Co., Ltd.) The heat-sealing conditions were a temperature of 170°C, a pressure of 4.0 MPa / cup, and a time of 0.8 seconds.

[0053] After cooling at room temperature, the laminate of the present invention was peeled off from the paper cup container at a 90-degree angle using a tensile tester (manufactured by Orientec Co., Ltd., trade name: Tensilon RTE-1210) to measure the strength of the force required for peeling. The pulling speed was 300 mm / min. The force required for peeling peaked immediately after opening began, and the strength at this peak was taken as the opening strength.

[0054] In addition, the peeled surface of the paper cup container after peeling the laminate was observed, and the degree of stringiness was visually observed (peeling appearance). The observation results were evaluated on a three-point scale: ○ (almost no stringiness, good appearance), △ (a small amount of stringiness occurred), and × (a large amount of stringiness occurred, poor appearance). The observation results of ○ and △ were judged to be good.

[0055] Table 1 shows the results of film cracking, thickness accuracy, and necking as evaluations of molding processability, and the results of measurements of opening strength and peel appearance as evaluations of adhesive properties.

[0056] Example 2 Thermoplastic resin pellets and laminates were prepared in the same manner as in Example 1, except that the processing temperature was 200°C instead of 180°C in the same thermoplastic resin pellet preparation method as in Example 1, and evaluation of molding processability, measurement of opening strength, and evaluation of opening appearance were performed. When the obtained easily peelable adhesive pellets were cut near the center parallel to the flow direction, the average major axis of the elliptical domains that appeared on the cut surface was 10 μm, and the ratio of the domain major axis to the domain minor axis (major axis / minor axis) was 3. The results are shown in Table 1.

[0057] Example 3 In the same thermoplastic resin pellet production method as in Example 1, a screw configuration with medium mixing specifications with two kneading sections was used instead of a screw configuration with weak mixing specifications with one kneading section, and a processing temperature of 200 ° C instead of 180 ° C. Thermoplastic resin pellets and laminates were produced in the same manner as in Example 1, and evaluation of molding processability, measurement of opening strength, and evaluation of opening appearance were performed. When the obtained easily peelable adhesive pellets were cut near the center parallel to the flow direction, the average major axis of the elliptical domains appearing on the cut surface was 6 μm, and the ratio of the domain major axis to the domain minor axis (major axis / minor axis) was 9. The results are shown in Table 1.

[0058] Example 4 Thermoplastic resin pellets and laminates were prepared in the same manner as in Example 1, except that the processing temperature was 200°C instead of 180°C and strand cutting equipment was used instead of underwater cutting equipment, and evaluation of molding processability, measurement of opening strength, and evaluation of opening appearance were performed. When the obtained easily peelable adhesive pellets were cut near the center parallel to the flow direction, the average major axis of the elliptical domains appearing on the cut surface was 10 μm, and the ratio of the domain major axis to the domain minor axis (major axis / minor axis) was 10. The results are shown in Table 1.

[0059] Example 5 Thermoplastic resin pellets and laminates were prepared in the same manner as in Example 4, except that the blending ratio of thermoplastic resin (E) and thermoplastic resin (F) was 80 / 20 by weight instead of 65 / 35 by weight in the same manner as in Example 4, and evaluation of molding processability, measurement of opening strength, and evaluation of opening appearance were performed. When the obtained easily peelable adhesive pellets were cut near the center parallel to the flow direction, the average major axis of the elliptical domains appearing on the cut surface was 10 μm, and the ratio of the domain major axis to the domain minor axis (major axis / minor axis) was 10. The results are shown in Table 1.

[0060] Example 6 Thermoplastic resin pellets and a laminate were prepared in the same manner as in Example 2, except that the thickness of the intermediate layer (B) was 32 μm instead of 25 μm and the thickness of the seal layer (A) was 8 μm instead of 15 μm, and evaluation of molding processability, measurement of opening strength, and evaluation of opening appearance were carried out. The results are shown in Table 1.

[0061] Comparative Example 1 In the same thermoplastic resin pellet production method as in Example 1, except that a screw configuration with medium mixing specifications having two kneading sections was used instead of a screw configuration with weak mixing specifications having one kneading section, thermoplastic resin pellets and laminates were produced in the same manner as in Example 1, and evaluation of molding processability, measurement of opening strength, and evaluation of opening appearance were performed. When the obtained easily peelable adhesive pellets were cut near the center parallel to the flow direction, the average major axis of the elliptical domains appearing on the cut surface was 4 μm, and the ratio of the domain major axis to the domain minor axis (major axis / minor axis) was 2. The results are shown in Table 2.

[0062] The obtained laminate had a lot of stringiness on the peeled surface, and the appearance after opening was poor.

[0063] Comparative Example 2 In the same thermoplastic resin pellet production method as in Example 1, a screw configuration with medium mixing specifications with two kneading sections was used instead of a screw configuration with weak mixing specifications with one kneading section, and a strand cutter was used instead of an underwater cutter. Thermoplastic resin pellets and laminates were produced in the same manner as in Example 1, and evaluation of molding processability, measurement of opening strength, and evaluation of opening appearance were performed. When the obtained easily peelable adhesive pellets were cut near the center parallel to the flow direction, the average major axis of the elliptical domains appearing on the cut surface was 4 μm, and the ratio of the domain major axis to the domain minor axis (major axis / minor axis) was 4. The results are shown in Table 2.

[0064] The obtained laminate had a lot of stringiness on the peeled surface, and the appearance after opening was poor.

[0065] Comparative Example 3 In the same thermoplastic resin pellet production method as in Example 1, except that a screw configuration with strong kneading specifications having three kneading sections was used instead of a screw configuration with weak kneading specifications having one kneading section, thermoplastic resin pellets and laminates were produced in the same manner as in Example 1, and evaluation of molding processability, measurement of opening strength, and evaluation of opening appearance were performed. When the obtained easily peelable adhesive pellets were cut near the center parallel to the flow direction, the average major axis of the elliptical domains appearing on the cut surface was 2 μm, and the ratio of the domain major axis to the domain minor axis (major axis / minor axis) was 18. The results are shown in Table 2.

[0066] The obtained laminate had low tear strength, and many strings were observed on the peeled surface, resulting in a poor appearance after opening.

[0067] Comparative Example 4 Thermoplastic resin pellets and laminates were produced in the same manner as in Example 4, except that a screw configuration with strong mixing specifications and three kneading sections was used instead of a screw configuration with weak mixing specifications and two kneading sections, and evaluations of molding processability, opening strength, and opening appearance were performed. When the obtained easily peelable adhesive pellets were cut near the center parallel to the flow direction, the average major axis of the elliptical domains appearing on the cut surface was 15 μm, and the ratio of the domain major axis to the domain minor axis (major axis / minor axis) was 18. The results are shown in Table 2.

[0068] The obtained laminate had a lot of stringiness on the peeled surface, and the appearance after opening was poor.

[0069] Comparative Example 5 Thermoplastic resin pellets and laminates were produced in the same manner as in Example 1, except that a single-screw extruder (PDA40, manufactured by Placo Co., Ltd.) was used instead of a twin-screw extruder, and a screw configuration with a strong kneading specification with one kneading section was used. The molding processability was evaluated, and the opening strength and opening appearance were measured. When the obtained easily peelable adhesive pellets were cut near the center parallel to the flow direction extruded from the die, the elliptical domains that appeared on the cut surface had an average major axis of 25 μm, and the ratio of the domain major axis to the domain minor axis (major axis / minor axis) was 10. The results are shown in Table 2.

[0070] The obtained laminate had low tear strength, and many strings were observed on the peeled surface, resulting in a poor appearance after opening.

[0071] Comparative Example 6 Thermoplastic resin pellets and laminates were prepared in the same manner as in Example 1, except that the processing temperature was 250°C instead of 180°C in the same thermoplastic resin pellet preparation method as in Example 1, and evaluation of molding processability, measurement of opening strength, and evaluation of opening appearance were performed. When the obtained easily peelable adhesive pellets were cut near the center parallel to the flow direction, the average major axis of the elliptical domains appearing on the cut surface was 30 μm, and the ratio of the domain major axis to the domain minor axis (major axis / minor axis) was 12. The results are shown in Table 2.

[0072] The resulting easily peelable adhesive pellets had poor moldability due to film cracking during molding, and a laminate for evaluation of adhesiveness could not be obtained.

[0073] [Table 1]

[0074] [Table 2]

Claims

1. A thermoplastic resin pellet comprising a thermoplastic resin (E) and a thermoplastic resin (F) incompatible with the thermoplastic resin (E), wherein the thermoplastic resin (E) is a polyethylene resin, and the thermoplastic resin (F) is at least one type selected from the group consisting of crystalline polybutene resin, crystalline polypropylene, crystalline ethylene-propylene copolymer, and crystalline ethylene-propylene-butene-1 copolymer, and wherein the thermoplastic resin pellet comprises 60 to 90 parts by weight of the thermoplastic resin (E) and 10 to 40 parts by weight of the thermoplastic resin (F) (the total of (E) and (F) is 100 parts by weight), and wherein when the pellet is cut parallel to the flow direction in which it is extruded from a die, the thermoplastic resin (E) forms a matrix phase and the thermoplastic resin (F) is dispersed in the matrix phase to form domain phases, and the thermoplastic resin pellet has a cut surface in which the average major axis of the domain phase is in the range of 5 μm to 20 μm, and the ratio of the domain major axis to the domain minor axis (major axis / minor axis) is in the range of 3 to 15.

2. Thermoplastic resin pellets as described in claim 1, characterized in that the thermoplastic resin (E) is low-density polyethylene.

3. Thermoplastic resin pellets as described in claim 1 or 2, characterized in that the thermoplastic resin (F) is crystalline polypropylene.

4. An easily peelable adhesive comprising the thermoplastic resin pellets according to any one of claims 1 to 3.

5. 4. The method for producing thermoplastic resin pellets according to claim 1, wherein the thermoplastic resin (E) and the thermoplastic resin (F) are mixed, melt-kneaded, and then produced using a pelletizing facility selected from the group consisting of an underwater cut facility, a strand cut facility, and a hot cut facility.

6. A laminate comprising a sealing layer (A), an intermediate layer (B), and a substrate (C) laminated in this order, wherein the sealing layer (A) comprises the easily peelable adhesive according to claim 4.

7. 7. The laminate according to claim 6, wherein the intermediate layer (B) is made of a polyethylene-based resin (D) having a melt mass-flow rate of 0.3 g / 10 min or more and less than 200 g / 10 min, the ratio of the thickness of the seal layer (A) to the sum of the thicknesses of the seal layer (A) and the intermediate layer (B) is 5% or more and less than 50%, and the thickness of the seal layer (A) is 1 μm or more and less than 20 μm.

8. 8. The laminate according to claim 6, wherein the polyethylene resin (D) constituting the intermediate layer (B) satisfies the following requirement (a): (a) The swell ratio (SR) calculated by dividing the diameter (D) of a strand extruded at a temperature of 235°C and an extrusion rate of 3 g / min using a melt indexer used in JIS K 7210 by the orifice diameter (D0) of the melt indexer is 1.7 or more and 3.0 or less.

9. 9. The laminate according to claim 6, wherein the polyethylene resin (D) constituting the intermediate layer (B) is a low-density polyethylene.

10. 10. The laminate according to claim 6, wherein the polyethylene resin (D) constituting the intermediate layer (B) is an ethylene-α-olefin copolymer.

11. A container lid material comprising the laminate according to any one of claims 6 to 10.

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