JPH04220446A - Stabilized polyethylene resin composition for film - Google Patents

Abstract

PURPOSE:To provide the title compsn. excellent in the thermal stability during molding and in the resistance to coloration. CONSTITUTION:100 pts.wt. polyolefin resin is compounded with 0.01-3.0 pts.wt. antiblocking agent having an accumulated content of acids having a solid-acid strength pKa of at least 4.8 of 250mumol/g or lower at the surface and an OH group content of 200mumol/g or lower at the surface, 0.01-3.0 pts.wt. phenol antioxidant, and 0.01-0.2 pt.wt. phosphorus antioxidant to give the title compsn.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin resin composition for film molding which has excellent thermal stability during molding and color resistance.

0002

BACKGROUND OF THE INVENTION Polyolefin films are used in a wide range of applications, including food packaging, textile packaging, pharmaceutical packaging, fertilizer packaging, miscellaneous goods packaging, agricultural covering materials, and construction.

[0003] Anti-blocking agents such as silica, talc, and zeolite are added to such polyolefin films in order to improve handling workability. In addition, when phenolic antioxidants such as 2,6-di-t-butyl-4-hydroxytoluene (BHT) are added to suppress changes such as decomposition and crosslinking during processing, yellowing occurs during long-term storage. This is a well-known fact, and it is also known to use a phosphorus stabilizer in combination to prevent yellowing.

For example, Japanese Patent Publication No. 56-25935 reports a method in which a specific organic phosphite compound is used in combination with an alkyl-substituted monophenol stabilizer. However, their preventive effects cannot be said to be sufficient, and yellowing has been observed depending on environmental conditions.

[0005] Yellowing components, for example, in the case of BHT, are caused by carbonyl compounds with conjugated double bonds such as the quinone structure or stilbenequinone structure that are self-oxidized to prevent the deterioration of the polyolefin. It is known to have a very large extinction coefficient, so even a trace amount of formation causes yellowing.

[0006] Preventing yellowing is of practical importance because a yellowed film impairs its commercial value.

[0007] Furthermore, it is known that even if the above-mentioned antioxidant is added to a polyolefin film, its original effect may not be exhibited and various defects may occur. For example, in the case of cross-linked polymers such as polyethylene, the polymer cross-links during processing, resulting in frequent fish eyes, and in the case of degradable polymers, such as polypropylene, the polymer decomposes during processing, resulting in smoke generation. In many cases, the cause of these problems is not clear.

[0008]

[Problems to be Solved by the Invention] In view of the current situation, the problem to be solved by the present invention is to provide a polyolefin resin composition for film molding that has excellent thermal stability during molding and color resistance. It's about doing.

[0009]

[Means for Solving the Problems] As a result of intensive studies, the present inventors found that solid acids are strong, and when the cumulative amount of acids with pKa of 4.8 or less exceeds 250 μmol/g, antioxidants, especially phosphorus-based antioxidants, are used. It was discovered that the anti-oxidation and anti-coloring effects are not expressed due to hydrolysis of the anti-blocking agent.Furthermore, when the amount of OH groups on the surface exceeds 200 μmol/g, the anti-blocking agent The present inventors have discovered that the radical scavenging performance of the polymer is significantly inhibited by adsorption on the surface and the restriction of the degree of freedom of molecular movement during processing, making it impossible to express the effect as an antioxidant, leading to the present invention.

That is, the present invention provides that (a) the solid acid strength pKa of the surface is 4.8 or less, the cumulative amount of acid is 250 μmol/g or less, and the amount of OH groups on the surface is 100 parts by weight of the polyolefin resin; 0.01 to 3.0 parts by weight of an anti-blocking agent having a concentration of 200 μmol/g or less, (b) 0.01 to 0.3 parts by weight of a phenolic antioxidant, and (c) a phosphorus antioxidant. This is a stabilized polyolefin resin composition for film forming, characterized in that it contains 0.01 to 0.2 parts by weight of the following.

Polyolefin resins used in the present invention include homopolymers such as polyethylene, polypropylene, polybutene-1, and poly-4-methyl-pentene-1, as well as ethylene-propylene copolymers and ethylene-butene-1 copolymers. Polymer, ethylene-4-methylpentene-1 copolymer, ethylene-hexene-1 copolymer, ethylene-octene-1 copolymer, ethylene-decene-1
copolymer, propylene-4-methyl-pentene-1 copolymer, propylene-butene-1 copolymer, decene-1-
Examples include 4-methyl-pentene-1 copolymer and ethylene-propylene-butene-1 copolymer. In the case of copolymers, copolymers containing α-olefin and polyunsaturated compounds such as conjugated dienes and non-conjugated dienes, or acrylic acid, methacrylic acid, vinyl acetate, etc., are also included. These polymers are acid-modified, such as α
, β-unsaturated carboxylic acid, alicyclic carboxylic acid, or a derivative thereof, and includes rubbery, fatty, and waxy polymers.

Among them, an ethylene/α-olefin copolymer consisting of ethylene and an α-olefin having 4 to 10 carbon atoms is preferred because it is recognized to be highly effective since it requires a large amount of antioxidant and anti-blocking agent. .

[0013] Furthermore, the anti-blocking agent (a) used in the present invention has a surface solid acid strength pKa of 4.8.
Silica, clay, talc, diatomaceous earth, feldspar, kaolin, zeolite, kaolinite, wollastonite, having a cumulative acid content of 250 μmol/g or less and a surface OH group content of 200 μmol/g or less, Examples include sericite, amorphous aluminosilicate, and amorphous calcium silicate.

[0014] Here, the solid acid strength pKa of the surface was measured by baking the anti-blocking agent at 150°C for 3 hours, allowing it to cool to room temperature in a silica gel desiccator, and then using Bene.
It was determined by si method by adsorption with n-butylamine and using a Hammett indicator.

Further, the amount of OH groups on the surface was measured by the following method. That is, the anti-blocking agent was vacuum-dried at 120°C for 2 hours and allowed to cool to room temperature in a silica gel desiccator. Approximately 2 g of the anti-blocking agent sample was weighed and placed in a dry 100 ml three-necked flask, and 40 ml of dehydrated toluene was added. Add.

After purging the system with dry N2 gas, a 11 vol % toluene solution of triethylaluminum was added while stirring with a magnetic stirrer, and the amount of ethane gas generated by the reaction between the OH group on the surface of the anti-blocking agent and triethylaluminum was determined. Then, the surface O
Calculate the H group amount (n).

n=PV/RTW [where n: surface OH group amount (mol/g), P: pressure (atm), V: ethane gas generation amount (l), R: gas constant (atm ・l/mol・degree K), T: temperature (degree K)
, W: sample weight (g)]

The amount of the anti-blocking agent (a) needs to be 0.01 to 3.0 parts by weight. If the amount added is less than 0.01 parts by weight, the anti-blocking properties of the film will not be improved, and if it exceeds 3.0 parts by weight, the transparency will decrease. In addition, from the viewpoint of anti-blocking effect and transparency, an anti-blocking agent having an average particle size of 0.3 to 8 microns and containing 5 vol % or less of particles with a particle size of 10 microns or more is a preferable anti-blocking agent.

[0019] Here, the average particle diameter refers to a value measured by using a Coulter counter and dispersing the anti-blocking agent in an electrolytic solution for 2 minutes using ultrasonic waves.

Next, as the phenolic antioxidant (b) used in the present invention, for example, 2,6-di-t-butyl-4
-Methylphenol, tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate (manufactured by Ciba Geigy, Irganox 3114), 2,2'-
Methylenebis(4-ethyl-6-t-butylphenol), n-octadecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate (manufactured by Ciba Geigy, Irganox 1076), 4, 4
'-thiobis(3-methyl-6-t-butylphenol), tetrakis[methylene-3-(3',5'-di-t
-butyl-4'-hydroxyphenyl)probionate] methane (manufactured by Ciba Geigy, Irganox 101
0), 4,4'-butylidenebis(3-methyl-6-t
-butylphenol), 2,2'-methylenebis(4-
Methyl-6-t-butylphenol), N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxyhydrocinnamide) (manufactured by Ciba Geigy, Irga
nox 1098), triethylene glycol-bis[
3-(3'-t-butyl-5'-methyl-4-hydroxyphenyl)propionate], bis(3,5-di-t
-butyl-4-hydroxybenzylphosphonate)
Mixture of calcium and PE wax (1:1 weight ratio)
etc. can be mentioned.

[0021] If the amount of the phenolic antioxidant (b) added is less than 0.01 part by weight, no antioxidant effect will be exhibited, and if it exceeds 0.3 part by weight, yellowing will be accelerated during long-term storage. This may cause the film to bleed onto the surface of the film, impairing its transparency, or deteriorating its blocking properties.
It is necessary that the amount is 0.01 to 0.3 parts by weight.

[0022] Further, as the phosphorus antioxidant (c),
For example, trimethyl phosphite, tri-n-butyl phosphite, tridecyl phosphite, tris(2-ethylhexyl) phosphite, trinonyl phosphite, tricetyl phosphite, dilauryl hydrogen phosphite, tricyclohexyl phosphite, triphenyl phosphite. , tribenzyl phosphite, tricresyl phosphite, tri-p-nonylphenyl phosphite, diphenyldecyl phosphite, tris(dinonylphenyl) phosphite, tris(2,4-di-t-butylphenyl) phosphite, tris( 4-α-Methylbenzylphenyl) phosphite, tris(octylthioethyl)phosphite, tris(octylthiopropyl)phosphite, tris(cresylthiopropyl)phosphite, tris(3,5-di-t-butyl-4-hydroxy) phenyl)phosphite, tetraphenyldipropylene glycol diphosphite, 4,4'-butylidenebis(3-methyl-6-t-butylphenyl-ditridecyl)phosphite, 1,1,3-tris(2-methyl-4- ditridecylphosphite-5-t-butylphenyl)butane, bis(2-chloropropyl)pentaerythritol diphosphite, bisphenylpentaerythritol diphosphite, bisstearylpentaerythritol diphosphite, trilauryl trithiophosphite, Examples include tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphite.

[0023] The amount of phosphorus antioxidant (c) added is 0.0
If the amount is less than 1 part by weight, no antioxidant effect or anti-yellowing effect will be exhibited, and if it exceeds 0.3 part by weight, there will be increased concerns about black speck and corrosion of metals.
It is necessary that the amount is 01 to 0.2 parts by weight.

In order to obtain the stabilized polyolefin resin composition for films of the present invention, the polyolefin resin and (a), (b) and (c) are mixed by a known method within the above range,
For example, a method of mixing with a tumbler blender, a Henschel mixer, etc., a method of melt-kneading and granulating with a single-screw extruder, a multi-screw extruder, etc. after mixing, a method of melt-kneading and granulating with a kneader, a Banbury mixer, etc. I can do it.

Furthermore, for example, polyolefin resin and (b
), (c) can be melt-kneaded and granulated by the above method, and a masterbatch obtained by melt-kneading and granulating the polyolefin resin and (a) can be added to obtain a composition within the above range.

In the present invention, commonly used lubricants,
Antistatic agents, weathering agents, UV agents, antifogging agents, pigments, etc. may be added to the extent that they do not impair the purpose of the present invention.

The stabilized polyolefin resin composition for film molding of the present invention can be processed by ordinary air-cooled inflation molding, air-cooled two-stage cooling inflation molding, T-die film molding, water-cooled inflation molding, etc. It is possible to make a film with excellent coloring resistance without impairing stability.

[0028]

[Examples] The present invention will be explained in detail below using Examples and Comparative Examples, but the present invention is not limited thereto. Note that the performance in Examples and Comparative Examples was measured by the following method.

(1) Fish eyes, smoke, and streak-like unevenness during processing of the heat-stable film were observed, and quality was determined by relative comparison using the same resin and under the same processing conditions. ○…The above defective phenomena are rare △… 〃 Moderate×… 〃
many

(2) Color resistance A sheet with a thickness of 2 mm was prepared, aged for 2 weeks at 60° C. and 90% RH, and the yellowness index (YI) was measured (JI
Compliant with SK7103). The lower the YI value, the better.

Examples 1 to 3, Comparative Examples 1 to 6 MFR=0.
8 g/10min, density=0.919 g/cm
3, 100 parts by weight of the ethylene-butene-1 copolymer, 0.2 parts by weight of anti-blocking agents with different solid acid strengths and OH group amounts on the surface, and 0 parts by weight of Sumilizer BP76 manufactured by Sumitomo Chemical Co., Ltd. as a phenolic antioxidant. .15 parts by weight and 0.10 parts by weight of Sand Starb P-EPQ (manufactured by Sandoz Co., Ltd.) as a phosphorous antioxidant were blended, and the pellets were melt-kneaded using a single-screw extruder. A 120 mmφ manispill type die was attached to the die, and the processing temperature was 200 with a lip gap of 2 mm.
℃ and BUR=2.0 to obtain a film with a thickness of 30 μm. Thermal stability during processing was evaluated, and a 2 mmt sheet was produced using the obtained film by a pressing method, and the YI value was determined by the accelerated test described above. The results are shown in Table 1.

Examples 4 to 6, Comparative Examples 7 to 10 MFR=5 with ethylene content of 2% by weight and butene-1 content of 6% by weight.
g/10min, melting point 138 °C, 100 parts by weight of propylene-ethylene-butene-1 copolymer, 0.3 parts by weight of anti-blocking agents with different surface solid acid strength and OH group content, and phenolic antioxidant. 0.1 part by weight of Sumilizer BP101 and 0.05 parts by weight of PEP-8 manufactured by Adeka Argus Co., Ltd. as a phosphorous antioxidant were blended, and the pellets were melt-kneaded using a uniaxial granulator and then processed into a 65 mmφ extruder manufactured by Sumitomo Heavy Industries, Ltd. (screw L/D=32), die width 600 mm, die lip 1
．． A 0 mm, straight manifold type T-die was attached, extrusion was carried out at a processing temperature of 230°C, and a film with a thickness of 50 μm was obtained by cooling and solidifying with a cooling roll at 25°C. Thermal stability during processing was evaluated, and a 2 mmt sheet was created by a pressing method using the obtained film, and the YI value was determined. The results are shown in Table 1.

[0033]

Effects of the Invention According to the present invention, a polyolefin resin composition is provided which has excellent thermal stability during film molding and coloring resistance.

[0034]

[0035]

Claims (2)

[Claims] Claim 1: Based on 100 parts by weight of polyolefin resin, (a) the solid acid strength pKa of the surface is 4.8 or less, the cumulative amount of acid is 250 μmol/g or less, and the amount of OH groups on the surface is 200 μmol/g; g 0.01 to 3.0 parts by weight of an anti-blocking agent, (b) 0.01 to 0.3 parts by weight of a phenolic antioxidant, and (c) 0.01 part by weight of a phosphorus antioxidant. -0.2 part by weight of a stabilized polyolefin resin composition for film forming. Claim 2: The polyolefin resin is ethylene/α consisting of ethylene and an α-olefin having 4 to 10 carbon atoms.
- The stabilized polyolefin resin composition for film forming according to claim 1, which is an olefin copolymer.