JPS6341945B2 - - Google Patents

Description

[Detailed description of the invention]

[] Object of the Invention The present invention relates to an ethylene copolymer composition. More specifically, it relates to an ethylene polymer composition comprising (A) an ethylene-vinyl acetate copolymer and (B) a copolymer of ethylene and α-olefin having specific physical properties, and which can be heat-sealed at low temperatures. The object of the present invention is to provide a composition with excellent properties such as hardness, hot-tack properties, rigidity, and impact resistance. [] Background of the Invention Copolymers of ethylene and vinyl acetate have excellent heat-sealing properties such as low-temperature heat-sealing properties, contamination sealing properties, and hot-tack properties, as well as impact strength, so they can be used for dry lamination, extrusion lamination, multilayer films, and Widely used for applications such as injection molding. In order to fully exhibit these physical properties, the vinyl acetate content should be 5 to 20% by weight.
Copolymers of ethylene and vinyl acetate are commonly used. However, in the case of a copolymer of ethylene and vinyl acetate, the higher the content of vinyl acetate, the better the above-mentioned physical properties (heat sealability, impact strength) are. On the other hand, not only does the cost of raw materials increase, but the "firmness of the film or the rigidity of the molded product" (hereinafter referred to as "rigidity") becomes weaker, and the heat resistance also decreases, so the usage temperature of the molded product decreases. There are also natural restrictions on this. [] Structure of the Invention Based on the above, the present inventors conducted various searches to obtain a composition with good heat sealability, impact resistance, and rigidity. % copolymer of ethylene and vinyl acetate” (hereinafter referred to as “EVA”)
) and (B) has a density of 0.905 to 0.940g/cm ³ and a melting point of 106
~130℃, Melt Index (JIS)
Measured according to K-6760 at a temperature of 180℃ and a load of 2.16Kg (hereinafter referred to as 〓MI〓)
is 0.01 to 100 g/10 min, and the number of side chain alkyl groups having 1 to 10 carbon atoms is substantially the same as the main chain carbon atoms.
``Copolymer of ethylene and α-olefin with 3 to 35 pieces per 1000'' (hereinafter referred to as ``ethylene copolymer'')
It is a composition consisting of
We discovered that an ethylene polymer composition with an EVA composition ratio of 40 to 90% by weight not only has excellent heat sealability and impact resistance, but also has good rigidity. The invention has been achieved. [] Effects of the Invention The composition obtained by the present invention not only has excellent heat sealability and rigidity, but also exhibits the following characteristics (effects). (1) Relatively good impact resistance at normal temperatures. (2) It also has good heat resistance. (3) Excellent workability (formability). (4) Good impact resistance at extremely low temperatures (-40°C). The composition obtained by the present invention not only has excellent heat-sealability and rigidity as described above, but also exhibits the above-mentioned effects, so it can be used in a wide variety of fields. Above all,
Because it has good processability, it can be formed into packaging films and used in a wide variety of applications, including the following. (1) Inner layer of the bag made of multilayer blown film (2) Inner layer of the bag made of multilayer T-die film (3) Constituent layers of dry laminate film (4) Constituent layers of extruded laminate film (5) Composition of the present invention Single-layer film [] Detailed Description of the Invention (A) EVA The EVA used in the present invention is produced by copolymerizing ethylene and vinyl acetate using a free radical generator (for example, an organic peroxide). This is what you get. The content of vinyl acetate contained in this EVA is 5 to 30% by weight, and 8 to 30% by weight.
is preferred, particularly 12 to 25% by weight. If EVA with a vinyl acetate content of 5% by weight or less is used, the heat sealability and impact resistance of the resulting composition will be low. On the other hand, more than 30% by weight
When EVA is used, the rigidity is low, the transparency of the film is significantly reduced, and the impact resistance is also poor. For these reasons, no matter which EVA is used, there are problems when using it for the above-mentioned purposes. The MI of EVA used in the present invention is generally 0.1 to 50 g/10 min, particularly 0.5 to 50 g/10 min.
30g/10 minutes is preferable. This EVA is usually
It is obtained by copolymerization at a polymerization temperature of 150 to 260°C and a polymerization pressure of 1000 to 2000 kg/cm ² . (B) Ethylene copolymer The density of the ethylene copolymer used in the present invention is 0.905 to 0.940 g/ ^cm3 , and 0.910 to
0.935g/ ^cm3 is preferable, especially 0.915~
0.930g/cm ³ is preferred. Density is 0.905g/
When using ethylene copolymer with ^cm3 or less,
EVA rigidity improvement becomes insufficient. on the other hand,
Use of an ethylene copolymer of 0.940 g/cm ³ or more is undesirable because low-temperature heat-sealability and impact resistance will be greatly reduced. In addition, the melting point of this ethylene copolymer is 106~
130°C, preferably 114 to 127°C, and particularly preferred is an ethylene copolymer having a melting point of 117 to 125°C. On the other hand, when an ethylene copolymer having a melting point of 106° C. or lower is used, the effect of improving stiffness is small and the resulting composition has poor heat resistance. On the other hand, when an ethylene copolymer having a melting point of 130° C. or higher is used, the low-temperature heat-sealability and impact resistance are greatly reduced, and the improvement effect of the present invention becomes insufficient. Furthermore, the MI of this ethylene copolymer is 0.01
~100 g/10 minutes, preferably 0.1 to 50 g/10 minutes, particularly preferably 0.5 to 25 g/10 minutes. When an ethylene copolymer with an MI of 0.01 g/10 minutes or less is used, the processability of the composition is low. On the other hand, if an ethylene copolymer of 100 g/10 min is used, the impact resistance will be greatly reduced, which is not preferable. In addition, the side chain of the ethylene copolymer is substantially an alkyl group having 1 to 10 carbon atoms, and the number of alkyl groups in the side chain is 3 to 35 per 1000 carbon atoms in the main chain. Generally, the number is 5 to 30. It is not preferable to use an ethylene copolymer having three or more alkyl groups in the side chain because the low-temperature heat-sealability and impact resistance will be greatly reduced. on the other hand
It is not desirable to use an ethylene copolymer containing 35 or more ethylene copolymers because the effect of improving stiffness is insufficient. This ethylene copolymer uses a so-called carrier-supported catalyst obtained by supporting a transition metal compound (for example, titanium tetrachloride) or a transition metal compound on a carrier (for example, a compound containing magnesium) as the main catalyst, Furthermore, an organometallic compound (for example, an organoaluminum compound) is used as a cocatalyst, and in the presence of a so-called Ziegler catalyst obtained from these or a so-called Phillips catalyst whose main catalyst is chromium oxide supported on a carrier, ethylene and carbon atoms are combined. is at most 12 α−
It can be obtained by copolymerizing with olefin. The above catalysts are widely known, and the polymerization temperature is generally 50 to 250°C. This copolymerization is carried out in the presence of a solvent (eg, an aliphatic or cycloaliphatic hydrocarbon) or a solvent. Furthermore, typical examples of α-olefins used are:
Mention may be made of propylene, butene-1, hexene-1, octene-1 and 4-methylpentene-1. (C) Composition ratio (content ratio) The composition ratio of EVA in the composition obtained by the present invention is 40 to 90% by weight, preferably 40 to 80% by weight, and particularly preferably 50 to 80% by weight. be. If the composition ratio of EVA in the composition is 40% by weight or less,
Heat-sealability and impact resistance are greatly reduced,
The effects of the present invention cannot be obtained. On the other hand, if it exceeds 90% by weight, the rigidity will not be sufficiently improved and there will be no difference in physical properties from EVA alone. (D) Mixing method In producing the composition of the present invention, the above-mentioned
It can be obtained by uniformly mixing EVA and an ethylene copolymer, but it can also be obtained by homopolymerizing EVA or ethylene or copolymerizing ethylene and α-olefin. The compositions of the present invention contain additives such as anti-aging agents, antioxidants, ultraviolet absorbers, plasticizers, lubricants, fillers, antistatic agents, flame retardants and transparency improvers commonly used in The above-mentioned properties may be blended to such an extent that there is no substantial loss. Mixing methods include dry blending using a Henschel mixer, which is commonly used in the olefin resin industry, and melting using a mixer such as a Banbury mixer, kneader, roll mill, and screw extruder. One method is kneading. At this time,
A more uniform composition can be obtained by dry blending or melt kneading in advance and further melt kneading the resulting mixture (composition). Further, a masterbatch is prepared by mixing a part of EVA and ethylene copolymer, which are components of the composition, or these and the above-mentioned additives, and other composition components are mixed with this masterbatch to produce a masterbatch. A composition may be manufactured. In these cases, the mixture is generally melt-kneaded and then formed into pellets, which are then subjected to the forming described later. (E) Molding method, etc. The composition obtained by the present invention can be molded into various molded articles by molding methods commonly used in the field of olefin resins.
Molding methods include injection molding, blow molding, extrusion molding, and compression molding, in addition to the inflation method and T-die method to mold single-layer films, multilayer films, and extrusion laminates. It will be done. Examples of molded products include film-like products, mat-like products, sheet-like products, lattice-like products, tube-like products, and hollow containers. When the composition of the present invention is produced by the above-mentioned melt-kneading method, and furthermore, in order to produce a molded article by these molding methods, it is necessary to It goes without saying that the process must be carried out at a temperature lower than the temperature at which these copolymers undergo thermal deterioration. from these things,
The melt-kneading temperature and molding temperature are usually 130 to 250°C. The composition of the present invention not only has good heat-sealing properties such as low-temperature heat-sealing properties and hot-tack properties, but also has excellent impact resistance and high rigidity. By making it possible to reduce the basis weight of Therefore, it is useful not only as an inner layer film for packaging of products containing liquid products such as various pickles and various liquid soups, but also for packaging of powdered substances such as various powdered soups, frozen foods, long-term storage foods, and packaging. It is most suitable as an inner layer film, and can be molded as a single layer or multilayer film by the inflation method or T-die method, or can be formed into other base films by the extrusion lamination method or dry lamination method. It is also possible to use it by attaching it to a material. Other examples of uses include various types of mats such as entrance mats, automobile floor mats, and draining mats formed by injection molding. These mats are generally required to have impact resistance and appropriate rigidity, and the composition of the present invention can provide a product that is much superior to EVA alone. [] Examples and Comparative Examples The present invention will be explained in more detail below using Examples. In addition, in Examples and Comparative Examples, each measurement item was measured by the following method. [Low-temperature heat sealability] Cut a 15 mm wide test piece in the longitudinal direction of the film, and use a heat sealer (manufactured by Tester Sangyo Co., Ltd.) to seal at a sealing pressure of 2 kg/cm ² and a sealing time of 1.
Seal by changing the heat sealing temperature under the conditions of seconds,
The seal strength was measured using an Instron type tensile tester at a chuck distance of 50 mm, a tensile speed of 500 mm/min, and a temperature of 23°C, and the temperature at which a seal strength of 500 g/15 cm width was obtained was determined. [Hot-tackability] Using a heat sealer for hot-tack measurement (manufactured by Tester Sangyo Co., Ltd.), heat-seal a film with a width of 5 mm and a length of 30 cm under conditions of a sealing pressure of 2 kg/cm ² and a sealing time of 1 second. , immediately after sealing
It was instantly pulled in the longitudinal direction with a load of 40 g, and the peeling length of the sealed portion was measured at each sealing temperature, and the range of sealing temperatures where the peeling length was 1 cm or less was taken as a guideline for hot-tack properties. Therefore, the wider the temperature range, the better the hot-tack properties. [Film tensile impact strength] Measurement was performed at a temperature of 23°C in the longitudinal direction (M direction) and transverse direction (T direction) of the film according to the test method of JIS K-6760. [-40°C tensile impact strength] A press sheet (thickness: 1.5 mm) was punched out into a type S dumbbell, the sample was adjusted to a temperature of -40°C, and immediately measured according to the test method of JIS K-6760. [2% modulus] Sample the film at a width of 20 mm in the longitudinal and transverse directions, and use an Instron tensile tester to test the stress at 2% deformation when the chuck distance is 250 mm and the tensile speed is 5 mm/min. It is expressed as The physical properties of EVA and ethylene polymer used as polymeric substances in Examples and Comparative Examples are shown below. [EVA] Table 1 shows the vinyl acetate content, MI and abbreviation of the EVA used.

[Ethylene polymers, etc.]

In addition, the type of ethylene polymer used and the α-olefin used as a comonomer for the high density ethylene polymer, MI, density, number of side chain alkyl groups per 1000 main chain carbon atoms, and the alkyl group. Table 2 shows the average carbon number and melting point of .

[Table] Examples 1 to 6, Comparative Examples 1 to 5 EVA and ethylene polymer whose blending amounts are shown in Table 3 were used as polymeric substances, and 2,6-di-tertiary was used as a stabilizer. class-butyl-4
- 0.05 parts by weight of methoxyphenol, 0.1 parts by weight of natural silica as a filler and 0.1 parts by weight as a lubricant;
Parts by weight of oleic acid amide were used in each of the Examples and Comparative Examples, and the mixtures were melt-kneaded using a Banbury mixer at 120-150°C for 3 minutes. Each of the obtained mixtures was extruded using an extruder (screw diameter 300 mm, L/D 10) to produce pellets. The screw diameter of each pellet obtained is
Using a 50mm, L/D 26 blown film manufacturing device, resin temperature is 155℃, blow ratio is 1.5.
and the thickness is 30 m/min.
Manufactured micron film. The low-temperature heat-sealing properties, hot-tack properties, film tensile impact strength, tensile impact strength at -40°C and 2% modulus of each film obtained were measured. The results are shown in Table 4.

【table】

【table】

[Table] From the results of the above Examples and Comparative Examples, it is clear that the compositions obtained by the present invention have excellent mechanical properties such as low-temperature sealing properties, hot-tack properties, and impact resistance. Furthermore, the compositions of the invention have approximately the same content of vinyl acetate.
Of these mechanical properties compared to EVA alone,
It is clear that both have been significantly improved and that there are some benefits to be gained by making compositions from EVA and ethylene-based polymers.

Claims (1)

[Scope of Claims] 1 (A) an ethylene-vinyl acetate copolymer containing 5 to 30% by weight of vinyl acetate; and (B) a density of 0.905 to 0.940 g/cm ³ and a melting point of 106
~130°C with a melt index of 0.01
~100g/10min, and the number of side chain alkyls having substantially 1 to 10 carbon atoms is the main chain carbon atom
It is a composition consisting of a copolymer of ethylene and α-olefin with 3 to 35 copolymers per 1000 pieces, and the ethylene-
An ethylene polymer composition in which the composition ratio of vinyl acetate copolymer is 40 to 90% by weight.