JPH0256372B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a resin composition for extrusion molding. More specifically, the present invention relates to an extrusion molding resin composition suitably used for extrusion molding of packaging films and the like. Currently, there is a wide variety of packaging materials used for packaging foods, medicines, miscellaneous goods, industrial goods, etc., but most of them are made of low-density polyethylene, polypropylene, and ethylene-vinyl acetate copolymers produced by radical polymerization. , a polyolefin resin such as an ionically crosslinked ethylene-acrylic acid copolymer (ionomer resin) is used as its heat seal layer. These resin layers are usually used by being laminated with other suitable base films. When producing a laminated film, bonding with adhesives, coextrusion, extrusion coating, dry lamination, etc. are applied during its production. By the way, packaging materials are originally designed to have tensile strength, tear strength, impact strength,
Mechanical strength such as heat seal strength, barrier function such as moisture proofing and gas barrier properties,
Many functions are required, including thermal properties such as heat resistance and cold resistance, as well as packaging machine adaptability such as heat sealability, hot tack, rigidity, and slip resistance. In the case of laminated films, the above-mentioned performance changes significantly depending on the selection of the base material, but similarly, the functionality of the packaging material changes significantly depending on the selection of the type of resin used for the heat-sealing layer. For example, the following facts are shown regarding the characteristics of packaging materials manufactured by dry laminating various polyolefin films on stretched polyamide (nylon) films. In other words, when a high-pressure low-density polyethylene film is used as the heat-sealing layer, this laminated film can be heat-sealed at temperatures above about 110°C, and is superior in terms of heat-sealing strength, impact bag-breaking strength, and rigidity. Provides a reasonably balanced packaging material. However, in automatic filling packaging, when the contents are filled immediately after being heat-sealed and the weight is applied to the sealed part that has not yet been sufficiently cooled and solidified, the hot tack, which indicates the sealing performance, is low. Density polyethylene film is not very good. In addition, when polypropylene is used for the heat-sealing layer, the heat-sealing start temperature is approximately 30 to 40°C higher than that of low-density polyethylene, which is disadvantageous for high-speed filling, and the heat of the base material and printing ink increases. It has potential problems such as causing deterioration. Furthermore, although it is superior to low-density polyethylene in terms of rigidity and hot-tack, it has low impact tear strength and is not necessarily suitable for packaging liquids. When an ethylene-vinyl acetate copolymer is used in the heat-sealing layer, the heat-sealing temperature is more than 10°C lower than when low-density polyethylene is used.
Although it has high heat seal strength and impact bag tear strength, it has low rigidity and softness, and is inferior in hot tack. In addition, when an ionically crosslinked ethylene-acrylic acid copolymer (ionomer resin) is used for the heat seal layer, it has improved low-temperature heat sealability, heat seal strength, and hot tack compared to when low density polyethylene is used. Although it is extremely superior and also excellent in impact bag breakage strength, it is not as good as ethylene-vinyl acetate copolymer. As described above, even if we compare the characteristics of various polyolefin resins that are currently generally used for the heat seal layer of laminated packaging materials, they all have advantages and disadvantages, and are not necessarily satisfactory. The present invention aims to provide a resin composition for extrusion molding that eliminates all the drawbacks of polyolefin resins used as heat sealing layers of such packaging materials, and this resin composition can be suitably used for extrusion molding. For example, it may be extrusion coated onto a base film to form a heat seal layer thereon, or it may be extrusion molded into a single film or a composite film. The applicant has previously proposed (a) low-density polyethylene with a density of 0.91 to 0.94 g/cm ³ obtained by high-pressure radical polymerization, (b) ethylene-α with a density of 0.91 to 0.95 g/cm ³
- Olefin copolymer and (c) density 0.85 to 0.90
g/cm ³ of a low-crystalline to non-crystalline ethylene-α-olefin copolymer uniformly melt-mixed (Japanese Unexamined Patent Publication No. 174329/1983) and the above component (a). and (Japanese Unexamined Patent Publication No. 195135/1982) have proposed a resin composition for extrusion molding, which is obtained by uniformly melting and mixing the above-mentioned component (c) and tackifier (d). All of these resin compositions for extrusion molding fully achieve the intended purpose, but as a result of further study, it was found that each of the above components (a), (b), (c) and (d) was uniformly distributed. The resin composition for extrusion molding obtained by melt-mixing can sufficiently satisfy the performance required for the heat-sealing layer of packaging materials, such as low-temperature heat-sealability, heat-sealing strength, hot-tack, and bag-breaking strength.
Moreover, it has been found that it has excellent extrusion processability, and exhibits particularly excellent hot-tack over a wide heat-sealing temperature range from low to high temperatures. Therefore, the present invention relates to a resin composition suitably used for extrusion molding, etc., and this resin composition has (a) a density of 0.91 to 0.94 obtained by high-pressure radical polymerization;
about 10-60% by weight of low-density polyethylene in g/ ^cm3 , (b)
Approximately 20 to 70% by weight of ethylene-α-olefin ( ³ to 8 carbon atoms) copolymer with a density of 0.91 to 0.95 g/cm3, (c)
About 10 to 50% by weight of a low-crystalline to non-crystalline ethylene-α-olefin (3 to 4 carbon atoms) copolymer with a density of 0.85 to 0.90 g/cm ³ and (d) about 5 to 30% by weight of a tackifier. It has a melt index (190°C) of 1 to 30 g/10 minutes. The low-density polyethylene used as component (a) of the resin composition according to the present invention is generally produced under a reaction pressure of about 1000 to Polyethylene with a density of 0.91 to 0.94 g/cm ³ is obtained by radical polymerization under high pressure of 3000 atmospheres, and one of its characteristics is that when intermolecular chain transfer and double bonds in the main chain are involved in polymerization. One example is that the melt tension during melting is large due to the long chain branching that occurs. On the other hand, polyethylene obtained by polymerizing under medium to low pressure of about 1 to 100 atmospheres using metal oxide catalysts or Ziegler catalysts has virtually no long chain branches, so its melt tension is low. Very small.
In addition, ethylene-α-olefin copolymers, which are copolymerized by introducing various α-olefins as comonomers into this polymerization process, also do not have long chain branches.
Therefore, its melt tension is small. This melt tension influences the extrusion molding processability of the resin, and if it is too small, the self-supporting properties of the molten film during film molding or extrusion coating molding will be low, causing film sway. On the other hand, if it is too large, there will be a problem in the spreadability of the molten film, and the film will easily break during high-speed molding. The melt index of the low density polyethylene used in the present invention is approximately 0.5 to 30.
Preferably, it is in the range of g/10 minutes. If the melt index is lower than this, the melt viscosity will be too high and film breakage will occur easily, while if it is higher than this, the bag breakage strength and heat sealing strength will decrease, and at the same time there will be problems with film formation stability during molding. occurs. The ethylene-α-olefin copolymer of component (b) is a combination of ethylene and an α-olefin having 3 to 8 carbon atoms, such as propylene, butene-1, pentene-1, etc.
It is a copolymer with 1, hexene-1, octene-1, 3-methylbutene-1, 3,3-dimethylbutene-1, 4-methylpentene-1, etc., and 0.91
It has a density of ~0.95 g/ ^cm3 . Such copolymers are typified by chromium oxide, molybdenum oxide, titanium trichloride or titanium tetrachloride-alkylaluminum, titanium compounds such as titanium tetrachloride-magnesium compounds such as magnesium chloride-alkylaluminum (chloride), etc. Gas phase polymerization using various catalysts at medium to low pressures of approximately 1 to 100 kg/ ^cm2 ,
Manufactured by slurry polymerization, solution polymerization, etc. These copolymers have an α-olefin content of about 0.2-8 mol% and an α-olefin content of about 0.5-30 mol%.
Preferably it has a melt index of g/10 minutes. Low crystallinity or non-crystalline ethylene of component (c)
α-olefin copolymer has ethylene and 3 carbon atoms.
-4 alpha-olefins, such as propylene, butene-1, and has a density of 0.85-0.90 g/ ^cm3 . Such a copolymer is obtained by polymerizing using a composite catalyst of a vanadium compound represented by vanadium trichloride or vanadium tetrachloride and an organoaluminum compound, and preferably contains about 5 to 30 α-olefins. Copolymerization is carried out at a ratio of mol%. These copolymers desirably have a melt index within the range of about 0.5 to 30 g/10 minutes. These have low crystallinity (crystallinity by specific volume method is approx.
By using a non-crystalline ethylene-α-olefin copolymer (35% or less), the softening point of the resin composition is lowered, low-temperature heat-sealability and heat-sealing strength are improved, and impact resistance is also improved. Therefore, the bag breakage strength is improved. In addition, examples of the tackifier used as the component (d) include aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, aromatic hydrocarbon resins, polyterpene resins, rosins, and styrene resins. It will be done. Examples of aliphatic hydrocarbon resins include butene-
1, isobutylene, butadiene, 1,3-pentadiene, and other _C4 to _C5 mono- or diolefin-based polymers. Examples of alicyclic hydrocarbon resins include resins obtained by cyclizing and dimerizing diene components in subvent C ₄ - C ₅ fractions, resins obtained by polymerizing cyclic monomers such as cyclopentadiene, and aromatic resins. Examples include resins obtained by intranuclear hydrogenation of hydrocarbon resins. Examples of aromatic hydrocarbon resins include vinyltoluene, indene, α
-Resins containing _C9 vinyl aromatic hydrocarbons such as methylstyrene as a main component, and the like. Examples of polyterpene resins include α-pinene polymer,
Examples include β-pinene polymer, dipentene polymer, tenpene-phenol copolymer, and α-pinene-phenol copolymer. Examples of rosins include rosin, polymerized rosin, hydrogenated rosin, rosin glycerin ester and its hydrogenated product or polymerized product, rosin pentaerythritol ester and its hydrogenated product or polymerized product, and the like. Examples of styrene resins include styrene monomer polymers, styrene-olefin copolymers,
Examples include vinyltoluene-α-methylstyrene copolymer. Among these various tackifiers, aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, and styrene resins are particularly preferred from the viewpoint of color tone, odor, and the like. The addition of these tackifiers helps hot-tack the resin composition, especially at low heat-sealing temperatures (90-
It works extremely effectively to improve hot tack at temperatures (110℃). The resin composition of the present invention consists of (a) low density polyethylene, (b) ethylene-α-olefin (carbon number 3
~8) copolymer, (c) low-crystalline to non-crystalline ethylene-α-olefin (3 to 4 carbon atoms) copolymer, and (d) tackifier, each having component (a) of about 10 to 60
Weight%, component (b) is approximately 20 to 70% by weight, component (c) is approximately 10%
~50% by weight, and component (d) is used in a mixture of approximately 5~30% by weight. If the mixing ratio of component (a) is less than about 10%, the melt tension of the resin composition will be too low, and the molten film during extrusion will become unstable, causing fluctuations in film width and film thickness. If it is more than about 60%, the heat sealing strength, hot tack, and bag tearing strength that are aimed at in the present invention cannot be obtained, so neither is preferable. Regarding the mixing ratio of component (b), if it is less than about 20%, the heat sealing strength, hot tack, and bag tearing strength that are the objectives of the present invention cannot be obtained, and if it is more than about 70%, the resin pressure during extrusion molding is becomes high, making it impossible to obtain a high discharge rate, and at the same time, the melt tension of the molten film extruded from the die is too small, making the molten film unstable, and continuous stable productivity becomes difficult. If the mixing ratio of component (c) is less than about 10%, the desired low-temperature heat-sealability, heat-sealing strength, and bag-breaking strength of the present invention cannot be obtained, while if it is more than about 50%, the pellets after kneading will be There is a tendency for blocking, and furthermore, blocking problems occur in products after film processing or extrusion coating processing. Furthermore, if the mixing ratio of component (d) is less than about 5%, the hot-tack under the low heat-sealing temperature conditions that is the objective of the present invention cannot be obtained, while if the mixing ratio is about 30% or more, the Pellet tends to block, and at the same time, products after film processing or extrusion coating also become susceptible to blocking. The resin composition consisting of components (a), (b), (c) and (d) in such a mixing ratio must also have a melt index in the range of 1 to 30 g/10 minutes (190°C). . If the melt index is less than 1, the resin pressure during extrusion molding of the resin composition increases, not only does the motor load become excessive, but also the molten film coming out of the die is likely to break. On the other hand, if it is larger than 30, not only the heat sealing strength and the bag tearing strength will decrease, but also problems will arise in the stability of the molten film during molding. Thus, (a) of the specified mixing proportions,
Only a resin composition consisting of each component (b), (c), and (d) and having specified melting properties has excellent extrusion processing properties, and at the same time has various properties required as a heat seal layer. is fully satisfied. Regarding heat-sealing properties, the heat-sealing layer formed from this resin composition has ethylene-
It has low-temperature heat-sealing properties equivalent to or better than vinyl acetate copolymers, has heat-sealing strength that exceeds that of this copolymer and ionomer resins, and has hot-tack over a wide heat-sealing temperature range equivalent to that of ionomer resins. Furthermore, it exhibits a number of excellent properties, including superior bag-breaking strength compared to polyethylene and ionomer resins. A slip agent, an antiblocking agent, an antistatic agent, etc. can also be added to this resin composition, if necessary. Slip agents that can be used include, for example, higher fatty acids having 8 to 22 carbon atoms, metal salts thereof such as aluminum salts, calcium salts, and magnesium salts, or acid amides, stearic acid esters of saturated aliphatic alcohols, ethylene bis fatty acids (with 16 carbon atoms), ~18) Examples include amide. Examples of antiblocking agents include silica, calcium carbonate, and talc. Furthermore,
Examples of antistatic agents include glycerin esters of fatty acids having 8 to 22 carbon atoms, sorbitan esters,
Examples include sucrose ester and polyethylene glycol ester. The above components (a) to (d) and optionally added components can be mixed simultaneously or sequentially using a single screw extruder, twin screw extruder, Banbury mixer, various kneaders, etc. This is done using The mixed resin composition can be made into a film by extrusion molding such as inflation film molding or T-die casting, or it can be made into a film by extrusion molding such as inflation film molding or T-die casting, or it can be made into a film by extrusion molding such as inflation film molding or T-die casting molding, or it can be made into a film by extrusion molding such as inflation film molding or T-die casting molding, or it can be made into a film by extrusion molding such as inflation film molding or T-die casting molding. A multilayer coextruded film can also be obtained by coextrusion molding with other suitable resins such as a combined ionically crosslinked product (ionomer resin), polyamide, polyester, or polystyrene. Furthermore, the single film or coextruded film formed in this way can be used as a single or composite film or sheet of various plastics such as stretched or unstretched polypropylene film or sheet, polyamide film or sheet, stretched polyester film, aluminum foil, It is also possible to form a laminated film or sheet by dry lamination or sandwich lamination with cellophane, paper, etc., and the layer made of the resin composition of the present invention effectively acts as a heat-sealing layer. The resin composition according to the present invention can be extrusion-molded into a single film or various composite films or sheets as described above, but preferably it is extrusion-coated onto various substrates and a heat-sealing layer is applied thereto. It is desirable to form it. The extrusion coating can be used not only alone, but also as a coextrusion coating as in the case of forming the coextrusion film. Substrates to be extrusion coated include paperboard, paper, aluminum foil, and various plastic films and sheets used in lamination molding of the laminated films and sheets described above, and are applied according to general extrusion coating methods. be done. In this way, using the resin composition of the present invention,
Various laminated films or sheets on which a layer of this resin composition is formed by a lamination method or an extrusion coating method can be used to make sweets, snacks, etc. by using the layer as a heat-sealing layer.
Packaging of various foods such as dry foods such as instant ramen, furikake, and powdered soups, meat products such as ham, sausage, and cured meat, aquatic foods such as konnyaku, pickles, miso, and liquid soups, and liquid detergents and liquid medicines. It can also be effectively used by taking advantage of its properties such as excellent low-temperature heat-sealability, heat-sealing strength, hot-tack, bag-breaking strength, and suitability for automatic filling and packaging. Next, the present invention will be explained with reference to examples. Example 1 Density obtained by high-pressure radical polymerization method
0.917g/ ^cm3 low density polyethylene (melt index 7g/10 min) 30% by weight, density 0.920g/cm3
cm ³ of ethylene-4-methylpentene-1 copolymer (4-methylpentene-1 content 3.0 mol%, melt index 2 g/10 min) 30% by weight, density
20% by weight of low crystalline ethylene-butene-1 copolymer (butene-1 content 10 mol%, melt index 4 g/10 min) of 0.880 g/ ^cm3 and aliphatic carbonization with a ring and ball softening point of 100°C. In a mixture of 20% hydrogen resin,
1000 ppm of stearic acid amide was added as a slip agent, and the mixture was melt-kneaded at 140°C in a single-screw extruder to form pellets. The melt index of this uniformly mixed resin composition was 5.4 g/10 minutes. The resin composition pellets were melt-kneaded using an extruder with a diameter of 65 mm at a cylinder tip temperature of 295°C, and then extruded through a T-die to form a stretched nylon film prepared in advance using an isocyanate-based anchor coating agent. Extrusion coating of low density polyethylene (20μ thick) onto (15μ thick) polyethylene surface of laminated film, processing speed 40m/
The extrusion coating process was carried out under the condition that the coating thickness was 40 μm. At this time, the resin temperature directly below the die is
It was 285℃. The heat seal strength, hot tack strength and bag tear strength of the obtained three-layer laminate were measured using the methods described below, and the results are shown in Table 1 below. It is being [Measurement method] Heat seal strength: Heat seal pressure 2Kg/
cm ² , heat sealing time 0.5 seconds, tensile speed 300mm/
Hot-tack: A 45g weight is separately attached to the same end of two laminate samples via a guide roll, and after heat-sealing the samples, the seal bar is removed. At the same time as it separates, it touches the seal part.
The peeling force by the weight is applied at an angle of 23 degrees (this angle is set depending on the position of the guide roll on which the weight is applied), and at this time, the seal part is
Measure whether mm has peeled off Bag breaking strength: pressure 2Kg/cm ² , temperature 140℃, time 0.5
Heat-sealed and bag-made under conditions of 100 seconds
Examples 2 to 6 In Example 1, the composition of the resin composition was variously changed, Various characteristic values were similarly measured for the obtained three-layer laminate. As shown in Table 1 below, good results were obtained in all cases. Comparative Example 1 In Example 1, extrusion coating of only low density polyethylene was performed. As shown in the results in Table 1 below, compared to the extrusion coating laminate of the resin composition according to the present invention, the heat seal strength is lower, the low temperature heat sealability and hot tack are inferior, and the bag tear strength is also lower. It lacks suitability as a packaging material. Comparative Example 2 In Example 1, extrusion coating of only ethylene-4-methylpentene-1 copolymer was performed, but both ends of the molten film extruded from the T-die were not stable and had a constant width and thickness. It was not possible to obtain a suitable extrusion coating film. Comparative Example 3 In Example 1, extrusion coating of only the low-crystalline ethylene-butene-1 copolymer was performed, but both ends of the molten film extruded from the T-die were not stable and had a constant width and thickness. It was not possible to obtain a suitable extrusion coating film. Comparative Example 4 In Example 1, 70% by weight of low density polyethylene, 20% by weight of ethylene-4-methylpentene-1 copolymer, and low crystalline ethylene-butene-1 copolymer were prepared without using a tackifier. Extrusion coating of a resin composition with a coalescence content of 10% by weight was carried out. As shown in the results in Table 1 below, compared to the extruded coatein laminate of the resin composition according to the present invention, it is inferior in terms of low-temperature hot tack. Comparative Example 5 In Comparative Example 4, the content of low density polyethylene was changed to 60% by weight, and the content of ethylene-4-methylpentene-1 copolymer was changed to 30% by weight. Table 1 below
As shown in the results, compared to the extrusion coating laminate of the resin composition according to the present invention,
It has poor hot tack at a low heat-sealing temperature of 120°C, making it unsuitable as a packaging material. Comparative Example 6 In Example 1, 60% by weight of low density polyethylene and 60% by weight of low crystalline ethylene-butene-1 copolymer were used.
30% by weight and 10% by weight of aliphatic hydrocarbon resin
Extrusion coating of the resin composition was carried out. As shown in the results in Table 1 below, the hot tack is inferior compared to the extrusion coating laminate of the resin composition according to the present invention, so it lacks suitability as a packaging material. Comparative Example 7 Ethylene-vinyl acetate copolymer (EVA; vinyl acetate content 6% by weight, melt index 7
g/10 minutes), and extrusion coating was performed in the same manner as in Example 1 (however, the cylinder tip temperature was 245°C). As shown in the results in Table 1 below, compared to the extrusion coated laminate of the resin composition according to the present invention, it can be said that the low-temperature sealing performance and static pressure bag breaking strength are equivalent, but the hot-tack is inferior. Therefore, it lacks suitability as a packaging material.

【table】

[Table] Example 7 In Example 1, the density of low density polyethylene was 0.916 g/cm ³ and the melt index was 23 g/10.
30% by weight of ethylene-4-methylpentene-1 copolymer, 15% by weight of low-crystalline ethylene-butene-1 copolymer, ring and ball softening point
Mixed with 20% by weight of aliphatic hydrocarbon resin at 100℃, 1000ppm of oleic acid amide as a slip agent, and silica as an antiblocking agent.
A further 2000 ppm was added, mixed well, and melt-kneaded at 140°C using a single-screw extruder to form pellets. The melt index of this resin composition was 4 g/10 minutes. Extrusion coating using this resin composition
The same procedure as in Example 1 was carried out except that the coating thickness was 20 μm, and the heat seal strength and hot tack of the obtained three-layer laminate were measured, and the results are shown in Table 2 below. From this result, it is judged that this resin composition has sufficiently satisfactory performance as a heat seal layer resin for packaging materials. Table 2 Heat seal Heat seal strength Hot tack temperature (℃) (g/15mm width) (mm) 90 1105 9 100 2010 16 110 2705 18 120 3570 14 130 4200 16 140 4705 22 150 4675 32 160 4555 3 2 Example 8 Example Coextrusion coating was performed using the resin composition pellets used in Example 7. That is, this resin composition was kneaded using a 65 mm diameter extruder at a cylinder tip temperature of 295°C, and the resin temperature was
At 290°C, it was fed into one manifold of an in-die adhesive type two-layer coextrusion T-die. On the other hand, low-density polyethylene with a density of 0.917 g/cm ³ and a melt index of 7 g/10 minutes was kneaded using another 65 mm diameter extruder at a cylinder tip temperature of 320°C, and a resin temperature of 320°C. In this state, it was fed into the other manifold of the coextrusion T-die. In a coextrusion T die set at a temperature of 300℃, 2
After merging the two resin streams and laminating them, extrude them from the die exit so that the low-density polyethylene is on the side that is in contact with the base material, and apply it to a stretched nylon film base material (thickness 15μ) that has been coated with an isocyanate-based anchor coating agent in advance. On the other hand, the low density polyethylene layer is 20μ,
Further, coextrusion coating was performed at a processing speed of 80 m/min with a composition ratio of the resin composition layer of 20 μm. The heat seal strength and hot tack of the resulting three-layer laminate were measured. As shown in the results in Table 3 below, good characteristic values were obtained in all cases. Table 3 Heat seal Heat seal strength Hot tack temperature (℃) (g/15mm width) (mm) 90 995 11 100 2030 15 110 2890 18 120 3480 15 130 4450 15 140 4775 20 150 4850 28 160 4725 3 3

Claims (1)

[Claims] 1 (a) Density obtained by high-pressure radical polymerization method
0.91~0.94g/ ^cm3 low density polyethylene about 10~60
Weight %, (b) Ethylene-α with density 0.91-0.95 g/cm ³
-Olefin (3 to 8 carbon atoms) copolymer approximately 20 to 70
Weight %, (c) Low crystallinity to amorphous ethylene-α-olefin with density 0.85 to 0.90 g/cm ³ (C3 to
4) Approximately 10 to 50% by weight of the copolymer and (d) approximately 5 to 30% by weight of the tackifier are uniformly melt-mixed, and the melt index has a value of 1 to 30 g/10 minutes (190°C). Resin composition for extrusion molding. 2. The resin composition for extrusion molding according to claim 1, which is used for extrusion coating molding. 3. The extrusion molding resin composition according to claim 2, which is used for forming a heat seal layer. 4. The resin composition for extrusion molding according to claim 1, which is used for extrusion molding of films or sheets.