JPH07165841A - Polyethylene/aminoalkyl acrylate film and its production - Google Patents

Abstract

PURPOSE:To obtain a film having good strengths, good heat sealability, and high transparency. CONSTITUTION:This film is made of a polyethylene/aminoalkyl acrylate graft copolymer prepared by grafting 0.1-20 pts.wt. aminoalkyl acrylate compound represented by the formula (wherein R1 is hydrogen or methyl; R2 and R3 are each hydrogen or 1-4 C alkyl; and n is an integer of 1-4) onto 80.0-99.9 pts.wt. linear low-density polyethylene having a density of 0.895-0.935g/cm<3>, and has a haze of below 20%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene-aminoacrylate graft copolymer film having high strength, excellent transparency and good heat sealability, and a method for producing the same.

[0002]

2. Description of the Related Art A copolymer of ethylene and an α-olefin having 3 to 18 carbon atoms, which has a linear molecular structure,
Linear low-density polyethylene (hereinafter also referred to as “LLD”) having a density of less than 0.935 g / cm ³ has transparency, impact resistance, and high-density polyethylene (HDPE).
It has excellent creep resistance and impact resistance and creep resistance as compared with high-pressure low density polyethylene (LDPE), and is widely used in the fields of packaging materials, especially films and laminations.

However, linear low-density polyethylene as a film material has a problem that it is inferior in fluidity during melting and in moldability as compared with high-density polyethylene and high-pressure low-density polyethylene. That is, the linear low-density polyethylene has a very high Newton property at the time of flow, has a large shear stress in the high shear rate region, is likely to cause melt fracture at the time of molding, is inferior in high-speed moldability, and is poor in flowability at the time of molding. There was a problem that the required energy was large. In addition, the linear low-density polyethylene has a very small resistance force during melt elongation, that is, melt tension (melt tension), so that there is a problem that bubbles cannot be stably expanded during inflation molding.

In order to solve such problems, linear low-density polyethylene is blended with 10 to 50% by weight of high-pressure low-density polyethylene to form a film. When polyethylene is mixed with high-pressure low-density polyethylene, the fluidity or melt tension is slightly improved, but the excellent strength, transparency, and heat sealability inherent to linear low-density polyethylene film cannot be obtained stably. There is a new problem.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to obtain a film having good film strength and heat sealability and high transparency.

[0006]

[Means for Solving the Problems] The above problem is 0.895.
80.0 to 99.9 parts by weight of linear low-density polyethylene having a density of 0.935 g / cm ³ or more and the general formula

[Chemical 3] (Wherein R ₁ is hydrogen or a methyl group, R ₂ and R ₃ are hydrogen or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 4). A polyethylene-amino acrylate graft copolymer film formed by grafting 1 to 20 parts by weight and having a haze value of less than 20% is solved by a polyethylene-amino acrylate graft copolymer film. Hereinafter, the present invention will be described in detail.

The linear low-density polyethylene used in the present invention is a copolymer of ethylene and an α-olefin having 3 to 18 carbon atoms, preferably 3 to 8 carbon atoms. Carbon number 3
As the .alpha.-olefin of .about.18, propylene, butene-1,4-methyl-pentene-1, pentene-1, hexene-1, octene-1 and the like are used. These α
-The olefins are used alone or in combination.

The constituent unit derived from the α-olefin having 3 to 18 carbon atoms in the LLD is present in an amount of 1 to 7 mol%, preferably 1 to 5 mol%, more preferably 2 to 3 mol%. There is. When the constitutional unit derived from the α-olefin having 3 to 18 carbon atoms exceeds 7 mol%, impact resistance and creep resistance decrease, and when it is less than 1 mol%, transparency decreases.

The density of LLD is 0.895 to 0.935 g
/ Cm ³ , preferably 0.900 to 0.930 g / cm
³ , more preferably 0.910 to 0.925 g / cm
^{Is 3} . When the density is less than 0.895 g / cm ³ , impact resistance and creep resistance are reduced, and 0.935 g / c
When it exceeds m ³ , transparency is deteriorated.

The _Mw / _Mn of LLD is generally 1.5-4.
5, preferably 1.5 to 3.5. When M _w / M _n is less than 1.5, the fluidity (film formability) is reduced, and when M _w / M _n exceeds 4.5, the grain shape L of the aggregate of crystalline lamellas is larger than 700Å. A decrease in transparency can be seen. Here, the weight average molecular weight M _w and the number average molecular weight M
_n is determined by gel permeation chromatography.

The melt flow rate (MFR) of LLD at 190 ° C. is generally 0.01 to 90 g / 10 minutes, preferably 0.1 to 10 g / 10 minutes. When the melt flow rate is less than 0.01 g / 10 minutes, the fluidity (film moldability) is decreased, and when the melt flow rate is more than 90 g / 10 minutes, the melt tension (film moldability) is decreased. Melt flow rate is ASTM D1
It is a value measured according to 238E.

The polyethylene-amino acrylate graft copolymer according to the present invention comprises 80.0 to 99.9 parts by weight of LLD and 0.1 to 2 of aminoalkyl acrylate compound.
It is a graft of 0 parts by weight. The amount of LLD is 8
If it is less than 0.0 parts by weight, the tensile strength of the film is low,
If it exceeds 9.9 parts by weight, heat sealability and impact strength are poor.

The aminoalkyl acrylate compound used in the present invention has the general formula

[Chemical 4] R ₁ is hydrogen or a methyl group, and R ₂ and R ₃ are hydrogen or methyl, ethyl, n-
It is an alkyl group having 1 to 4 carbon atoms such as propyl, isopropyl and tertiary butyl. In addition, n represents an integer of 1 to 4, and specific examples of C _n H _2n include methylene, ethylene, trimethylene, tetramethylene, dimethylmethylene, methylethylmethylene, dimethylethylene, methyltrimethylene and the like. Specific examples of the aminoalkyl acrylate compound represented by the above general formula include aminomethyl acrylate, aminoethyl acrylate, amino normal butyl acrylate, N-methylaminoethyl acrylate, N-ethylaminoethyl acrylate and N-isopropylaminoethyl acrylate. , N-tert-butyl ethyl acrylate, N
-N-butylaminoethyl acrylate, N, N-dimethylaminomethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoisopropyl acrylate, N, N-dimethylamino-n-butyl acrylate, N, N -Dimethylaminohexyl acrylate, N, N-diethylaminoethyl acrylate, N, N-di-n-propylaminoethyl acrylate, N, N-diisopropylaminoethyl acrylate, N, N-di-n-butylaminoethyl acrylate, N -Methyl-N-ethylaminoethyl acrylate, N-methyl-Nn-butylaminoethyl acrylate, acrylic acid esters such as N, N-di-n-propylaminopropyl acrylate, and corresponding methacrylic acid ester It can be and listed.
Among the methacrylic acid esters, N, N-diethylaminoethyl methacrylate and N, N-dimethylaminoethyl methacrylate are preferable.

The polyethylene-aminoacrylate graft copolymer film of the present invention is prepared by reacting the above LLD and aminoalkyl acrylate compound in the presence of an organic peroxide directly in an extruder installed in the film forming machine to form the film. It can be manufactured by performing at the same time,
This method is also economical. As another method, a polyethylene-aminoacrylate graft copolymer is produced by using a kneading machine such as an extruder or a Banbury mixer or a radiation irradiation device,
This may be formed into a film by an ordinary film forming machine.

Examples of the organic peroxide include benzoyl peroxide, lauryl peroxide, azobisisobutyronitrile, dicumyl peroxide and t.
-Butyl hydroperoxide, α, α'-bis (t-
Butyl peroxydiisopropyl) benzene, di-t-
Butyl peroxide, 2,5- (t-butylperoxy) hexine and the like are preferably used.

The total amount of LLD and aminoalkyl acrylate compound is 100 parts by weight, and 0.005
It is used in an amount of 2.0 parts by weight, preferably 0.01 to 1 part by weight. If the amount of the organic peroxide added is less than 0.005 parts by weight, the modifying effect is not substantially exerted, and even if it is added in excess of 2.0 parts by weight, it is difficult to obtain further effects, and This may cause excessive decomposition or crosslinking reaction. The organic peroxide is decomposed by heating during the production of the polyethylene-aminoacrylate graft copolymer (hereinafter, sometimes simply referred to as a copolymer), and a part thereof is taken out of the copolymer and a part thereof is taken into the copolymer. It is considered difficult to accurately define the amount in the copolymer.

The grafting reaction and the film forming temperature for obtaining the above polyethylene-aminoacrylate graft copolymer are appropriately selected in consideration of the usual temperature conditions, that is, the deterioration of the resin, the decomposition temperature of the organic peroxide and the like. Generally, reaction temperatures in the range of 150 ° C to 250 ° C are used.

If necessary, a stabilizer, an antistatic agent, a coloring agent such as a pigment, and other additives are added to the polyethylene-aminoacrylate graft copolymer according to the present invention within a range not impairing the object of the present invention. can do. This addition may be made at the time of film formation or at the time of producing the polyethylene-aminoacrylate graft copolymer.

The polyethylene-aminoacrylate graft copolymer film of the present invention is formed by various known methods. For example, the air-cooled inflation method, the water-cooled inflation method, the T-die method and the like are suitable because the graft reaction is carried out in the extruder, and the air-cooled inflation method is particularly preferable.

The production of an air-cooled blown film can be carried out in an air-cooled blown film production apparatus, for example, LLD, an aminoalkyl acrylate compound and an organic peroxide are mixed and a circular extruder is used at a temperature of 150 to 250 ° C. It is extruded through a die, brought into contact with air blown out from an air-cooled air ring to be rapidly cooled, solidified, taken up by a pinch roll, and then wound on a frame. By this method, it is possible to simultaneously improve the transparency, strength and heat sealability of the air-cooled blown film, which has been difficult to solve at the same time.

Of course, in addition to the air-cooled blown film, a water-cooled blown film and a T-die process film can be produced, and a film having good transparency can be obtained.

The thickness of the polyethylene-aminoacrylate graft copolymer film of the present invention is 10 to 20 μm, more preferably 30 to 100 μm from the viewpoint of ease of use.
It is desirable that it is about m.

A haze value of 2 is obtained by the above manufacturing method.
A polyethylene-amino acrylate graft copolymer film having an excellent transparency of less than 0% can be obtained. The haze value is measured according to ASTM D1003. Further, in the present invention, the haze value indicates a numerical value obtained by summing the external haze value and the internal haze value.

[0024]

The polyethylene-amino acrylate graft copolymer film of the present invention has a particle size (L = 800 to 1100) of an aggregate of crystalline lamellas protruding in an irregular shape on the surface.
Å) is the particle size of high-density polyethylene (L = 500-70)
It has a feature of being smaller than 0Å), and can smooth the film surface and reduce the external haze value of the film. Furthermore, the grain size of the microcrystals inside the film is simultaneously reduced, and the internal haze value of the film can be reduced. Further, such a reduction in crystal grain size and an increase in molecular mobility lowers the melting temperature and develops a low-temperature heat-sealing property. Further, since the LLD component is 80.0 to 99.9 parts by weight, the high strength, which is an excellent property of the linear low-density polyethylene film, is maintained.

[0025]

【Example】

Examples 1 and 2 and Comparative Examples 1 and 2 By the air-cooled inflation molding method, LLD was reacted with an aminoalkyl acrylate compound in the presence of an organic peroxide directly in an extruder, and film molding was performed at the same time. As the organic peroxide, benzoyl peroxide was used in an amount of 0.1 part by weight based on 100 parts by weight of the total amount of LLD and the aminoalkyl acrylate compound. L
The LD used had a density of 0.950 g / cm ³ and a melt index of 0.04 g / 10 min, and aminoethyl acrylate was used as the aminoalkyl acrylate compound. The compounding ratio of LLD and aminoethyl acrylate was (95/5) in Example 1 and (90/1) in Example 2.
It was set to 0). In Comparative Examples 1 and 2, no aminoalkyl acrylate compound was used, and in Comparative Example 1, no organic peroxide was used. The composition having the above blending ratio was applied to an air-cooled inflation molding machine to give a thickness of 30 μm.
Was formed into a film. At that time, the molding temperature was 200 ° C and the blow ratio was 3
Met. The physical properties of the obtained film are shown in Table 1.

Each physical property was measured by the following methods. Haze value ・ ・ ・ Compliant with ASTM D1003 Yield strength ・ ・ ・ Compliant with JIS Z 1702 Young's modulus ・ ・ ・ Compliant with ASTM D882 Heat-sealing property ・ ・ ・ First, cut the film into a strip shape with a width of 15 mm and seal it. Pressure 2kg / cm
^2. Heat sealing is performed while changing the temperature under the condition that the sealing time is 1 second, and the test piece is peeled at a speed of 300 mm / min to examine the peel strength. As a result, the heat sealing property was represented by the sealing temperature of the test piece having a peel strength of 1 kg. Impact strength: Compliant with ASTM D781

From the results shown in Table 1, the film of the first invention has excellent impact strength, heat sealability, haze value,
It was confirmed that the material had well-balanced physical properties such as yield strength and Young's modulus.

[0028]

[Table 1]

[0029]

EFFECT OF THE INVENTION Since the polyethylene-aminoacrylate graft copolymer film described above has flexibility and an appropriate melting temperature, it has the excellent properties of linear low density polyethylene. In addition to strength, it also has good impact strength, heat sealability, and high transparency. Therefore, it can be easily heat-sealed at a low temperature, and is not easily broken even if it receives an impact. Further, according to the manufacturing method as described above, a film having high strength, easy heat sealability, high impact strength, and the like, and good transparency can be easily manufactured.

Claims (2)

[Claims] 1. A linear low-density polyethylene having a density of 0.895 or more and less than 0.935 g / cm ³ 80.0 to
99.9 parts by weight of the general formula: (Wherein R ₁ is hydrogen or a methyl group, R ₂ and R ₃ are hydrogen or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 4). A polyethylene-aminoacrylate graft copolymer film comprising a polyethylene-aminoacrylate graft copolymer grafted with 1 to 20 parts by weight and having a haze value of less than 20%. 2. A linear low-density polyethylene having a density of 0.895 or more and less than 0.935 g / cm ³ is represented by the general formula: (Wherein R ₁ is hydrogen or a methyl group, R ₂ and R ₃ are hydrogen or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 4). The method for producing a polyethylene-aminoacrylate graft copolymer film according to claim 1, wherein the graft copolymerization is carried out in a molding machine.