JP2003226786A - Polyethylene composition for resin-coated paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyethylene composition for a resin-coated paper, which has good high-speed molding and processing characteristics, yields little smoke, and can realize a product with good moistureproofness, heat resistance, etc. <P>SOLUTION: The polyethylene composition for a resin-coated paper is characterized by comprising a resin composition consisting of 5-40 pts.wt. of a high- pressure-processed low-density polyethylene which has a density of 930 kg/m<SP>3</SP>or lower, a melt mass flow rate of 0.5-3.0 g/10 min, a melt tension ratio, represented by the formula (1): MTR=(240&deg;CMT)/(190&deg;CMT) (1) (wherein MTR is melt tension ratio; and MT is melt tension), of 0.8 or higher, and of which the relation between the flow rate ratio and the melt tension satisfies the formula (2): (190&deg;CMT)&ge;0.65(FRR)-20 (20) (wherein MT is melt tension; and FRR is flow rate ratio), and 95-60 pts.wt. of a high-density polyethylene. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyethylene resin composition for coating one or both sides of a paper base material with a resin layer by an extrusion laminating method.
More particularly, the present invention relates to a polyethylene composition for resin-coated paper, which has excellent high-speed molding processability of the resin layer, good moisture resistance and heat resistance of the resin layer, and extremely low smoke emission during processing.

[0002]

2. Description of the Related Art It is common practice to coat one or both sides of a paper base material (hereinafter referred to as a paper base material) such as paper or paperboard with a resin capable of extrusion lamination molding. Resin-coated papers such as food packaging materials, moisture-proof papers, release papers, printing papers and photographic papers are well known. In these resin-coated papers, especially when moisture resistance and heat resistance are required,
It is well known that high-density polyethylene having a high melting point is often used for the resin layer, and the higher the density, the higher the moisture resistance and heat resistance. However, when a resin having a high density is used, in the laminating process when manufacturing the resin-coated paper, a phenomenon in which the resin film fluctuates or the thickness varies in the vertical and horizontal directions (hereinafter referred to as surging), the resin is extruded from a die. The resin film shrinks inward and becomes narrower (hereinafter referred to as neck-in), and problems such as film breakage occur.

Among these problems, there is a method of improving workability such as neck-in and surging by mixing with high-pressure low-density polyethylene.
JP-A 06-190983, JP-A 07-13435
9, JP-A 06-322189, JP-A 10-6019
No. 0, JP-A-10-60189. However, in recent years, further high-speed processability has been required to improve productivity. When a method of increasing the melt mass flow rate (hereinafter referred to as MFR) of high-density polyethylene is used to obtain high-speed processability, simply using a mixture of high-density polyethylene and high-pressure low-density polyethylene, fluctuations in thickness due to surging during high-speed processing , Membrane breakage, and excessive neck-in may be noticeable. Further, in order to improve these high-speed processability, it is possible to melt-mix high-pressure polyethylene having a low melt mass flow rate, but when the MFR of high-density polyethylene is high, gel-like defects may appear in the resin film. There is.

In order to obtain high-speed processability, it is an effective method to raise the processing temperature of the laminate, but gel-like defects may appear in the resin film. In particular, in high-density polyethylene, gel is very likely to be generated in the molten resin film during high temperature processing such as lamination molding. This gel not only becomes a projection on the surface of the coated paper and impairs the appearance, but may cause peeling due to defective printing or defective adhesion.

Further, in the high temperature and high speed processing as described above, among the low molecular weight components contained in the resin having a molecular weight of about 1000 or less, the components having a lower boiling point than the processing temperature become fumes and fill the periphery of the processing machine. However, not only does it adversely affect the environment, but components having a boiling point higher than the processing temperature tend to adhere to the surface of the cooling roll and stain the cooling roll. Particularly, when a lot of stains are generated on the cooling roll during a long-term operation, the adhesiveness between the cooling roll and the resin layer is increased, the peelability is deteriorated, and production may be difficult. As described above, the high-density polyethylene resin composition for resin-coated paper has excellent high-speed processability while maintaining the moisture resistance and heat resistance of the product, and is stable for a long period of time by suppressing smoke during processing. Providing a runnable polyethylene resin composition has been practically difficult.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a polyethylene resin-coated paper which has a very good high-speed molding processability of the resin layer and suppresses smoke generation during the process, thereby ensuring stable production over a long period of time. And a polyethylene resin composition for producing a resin-coated paper having high moisture resistance and heat resistance.

[0007]

DISCLOSURE OF THE INVENTION The present inventors have proposed a resin-coated paper having a polyethylene resin as a resin layer, which is a resin of high-density polyethylene having specific physical properties and high-pressure low-density polyethylene having specific physical properties. The inventors have found that the mixture can meet the above-mentioned purpose, and completed the present invention.

That is, the present invention provides (1) a resin composition comprising high-density polyethylene having a density of 950 kg / m ³ or more and high-pressure low-density polyethylene, wherein the high-pressure low-density polyethylene has a density of 930 k
Melt mass flow rate of 0.5 to 3 at g / m ³ or less.
0 g / 10 minutes, the melt tension ratio represented by the following formula (1) is 0.8 or more, the relationship between the flow rate ratio and the melt tension satisfies the following formula (2) 5 to 40 parts by weight, high A polyethylene composition for resin-coated paper, characterized in that the density polyethylene is 95 to 60 parts by weight. MTR = (240 ° C. MT) / (190 ° C. MT) (1) (190 ° C. MT) ≧ 0.65 (FRR) −20 (2) where MTR in the equations (1) and (2) is the melt tension ratio. , MT is melt tension, and FRR is flow rate ratio.

Here, the melt tension means the tension when polyethylene is extruded at 60 mm / min and pulled out at 2 mm / min using a nozzle capillary rheometer with a diameter of 2.0 mm. The flow rate ratio (hereinafter referred to as FRR) is MF specified by JIS K7210: 1999.
R (190 / 21.6) and MFR (190 / 2.16)
And FRR = MFR (190 / 21.6) / MFR (190
/2.16).

(2) The melt mass flow rate of high-density polyethylene is 30 g / 10 minutes to 60 g / 10 minutes, the density is 960 kg / m ³ or more, and the total of each component having 18 and 20 carbon atoms when extracted with chloroform is 400 ppm. A polyethylene composition for resin-coated paper according to (1) below. The quantitative determination of each component having 18 and 20 carbon atoms was performed as follows. 10 g of resin pellets and 40 cc of chloroform were put in a stainless steel container that can be closed, and after the container was closed, shaking extraction was performed in a warm bath at 85 ° C. for 2 hours. After cooling to room temperature, quantification was performed by gas chromatography. . Gas chromatographic determination was carried out using Shimadzu GC-9A, a 1.5 m column with OV-1 as a packing material, a constant temperature of 165 ° C., an injection temperature of 250 ° C., nitrogen as a carrier gas, and a detector. FID was used. The qualitative properties of each component were analyzed under the same conditions by using standard samples of octadecane and eicosane, and the retention time was used.

The present invention will be described in detail below. The high-pressure low-density polyethylene used in the polyethylene composition for resin-coated paper of the present invention has a density of 930 kg / m ³ or less and an MFR of 0.5 to 3.0 g / 10 minutes, preferably 0.5 to 2 It is in the range of 0.0 g / 10 minutes, the melt tension ratio represented by the formula (1) is 0.8 or more, and the relationship between the FRR and the melt tension satisfies the formula (2). Density is 930
When it exceeds kg / m ³ , workability is deteriorated, which is not preferable. When the MFR is less than 0.5 g / 10 minutes, gel is generated in the resin film during the laminating process, which causes a defect in the product, which is not preferable. If the MFR is 3g / 10 minutes or more,
It is not preferable because processing characteristics such as neck-in and high-speed processing property deteriorate.

If the melt tension ratio is less than 0.8, the effect of improving workability such as neck-in and surging is not recognized, and sufficient high-speed workability cannot be obtained, which is not preferable. Further, when the melt tension in the equation (2) is a relationship between the flare ratio and the melt tension, which is an index of the molecular weight distribution, when the melt tension is small, the effect of improving workability such as neck-in and surging is not recognized, and sufficient high-speed workability cannot be obtained. Not preferable.

In the present invention, the purpose of using the high-pressure process low-density polyethylene having a melt tension ratio of 0.8 or more is that the laminator process is often molded at a process temperature exceeding 300 ° C. In order to maintain the tension, it is to mix the resin whose melt tension has little temperature dependence. Good workability can be obtained even when the MFR is increased to obtain high-speed processing. High-pressure low-density polyethylene with high melt tension is required to obtain better processability, but it is generally known to broaden the molecular weight distribution in order to obtain a resin with high melt tension. However, it is difficult to obtain good processability with high-pressure low-density polyethylene having a broad molecular weight distribution, and it is preferable when the relationship between FRR, which is an index of the molecular weight distribution represented by the above formula (2), and melt tension is satisfied. It is possible to obtain excellent workability.

The high-pressure low-density polyethylene used in the polyethylene composition for resin-coated paper of the present invention is 1000 to
Ethylene polymerization obtained in the presence of a free radical generator such as peroxide under a high pressure of 3500 atm, which may be either an autoclave system or a tubular system, or a combination thereof. But it's okay. On the other hand, the high-density polyethylene used for the resin layer is
MFR is 30 to 60 g / 10 minutes, preferably 35 to 50
It must be in the range of g / 10 minutes and have a density of 950 kg / m ³ or more, preferably 960 kg / m ³ . If the MFR is less than 30 g / 10 minutes, high-speed workability cannot be obtained, and if it exceeds 60 g / 10 minutes, surging occurs during high-speed processing, which is not preferable. Density is 950k
When it is less than g / m ³ , moisture resistance and heat resistance are deteriorated, and defective cutting of the resin is likely to occur at the time of cutting the product, resulting in a defect of poor secondary workability.

Furthermore, in order to reduce the amount of smoke emitted during processing, it is necessary that the total of each component having 18 and 20 carbon atoms extracted with chloroform in the high-density polyethylene be 400 ppm or less. When the value exceeds 400 ppm, the amount of smoke generated during laminating becomes very large, stains are generated on the cooling roll due to the adhesion of the smoke generating component, and the adhesive force between the cooling roll and the resin layer increases, and the cooling roll and the resin layer May hinder the peeling property of. When the releasability deteriorates, the paper base material and the polyethylene resin film may be peeled off from each other, and deterioration of the product quality cannot be avoided.

The high-density polyethylene used in the present invention is polyethylene polymerized by single-stage polymerization using a Ziegler catalyst. A Ziegler catalyst is used as the catalyst for producing the high-density polyethylene used in the present invention. As the Ziegler catalyst, titanium, vanadium, zirconium, hafnium, cobalt, a compound containing at least one kind of transition metal among molybdenum, or a solid catalyst component obtained by supporting a compound containing these transition metals on a magnesium-containing compound or the like, There are known catalysts in combination with organometallic compounds. Specifically, Japanese Examined Patent Publication Nos. 50-32270 and 52-367.
88, No. 52-36790, and No. 52-36791.
No. 52-36792 and No. 52-3679.
4, gazette 52-36795 gazette, gazette 52-367.
96 publication, 52-36915 publication, 52-36.
917, 52-50070, 53-6.
No. 019, No. 56-43046, No. 57-1.
No. 9122, No. 61-24403, No. 61-
26805, 61-34445 and 61.
No. 50964, Japanese Patent Publication No. 3-58368, Japanese Patent Publication No. 2-42366, and Japanese Patent Laid-Open No. 10-218933.
The catalysts described in, etc. can be exemplified.

The high-density polyethylene used in the present invention uses the above Ziegler catalyst to carry out suspension polymerization, solution polymerization,
It can be produced by a known polymerization method such as gas phase polymerization. The high-density polyethylene resin used can be a mixture of resins produced separately, provided that it meets all the requirements mentioned above. As the polyethylene composition for resin-coated paper in the present invention, 5 to 40 parts by weight of the high-pressure low-density polyethylene having the above-mentioned physical properties and 60 to 95 having the above-mentioned physical properties are used.
It is a mixture of parts by weight of high density polyethylene.

If the proportion of the high-pressure low-density polyethylene resin component is less than 5 parts by weight, workability is deteriorated, which is not preferable. On the other hand, if it exceeds 40 parts by weight, the density of the composition after mixing becomes low, the product physical properties such as moisture resistance and heat resistance deteriorate, and the secondary processability such as cutting property deteriorates, which is not preferable. The above, high pressure method low density polyethylene 5-40
The parts by weight and the high density polyethylene 60 to 95 parts by weight are preferably melt-mixed compositions. As the melt mixing method, various commonly used ones can be used, and examples thereof include a single screw extruder, a twin screw extruder, a Banbury mixer, a pressure kneader, and a heating roll kneader.

Various additives can be mixed with the polyethylene composition for resin-coated paper of the present invention within a range that does not impair the effects of the present invention. For example, a heat stabilizer, an antioxidant and an ultraviolet absorber. Additives such as agents, fatty acid metal salts, antistatic agents, colorants and the like may be mixed. These additives can be mixed in advance during the production of the high-pressure low-density polyethylene and the high-density polyethylene, added at the time of mixing them, or added in a masterbatch system during processing.

The processing of the polyethylene composition for resin-coated paper according to the present invention is carried out by an extrusion laminating method, in which a film is formed from a slit die connected to an extruder on a paper base material prepared in advance. The resin is melt-coated. Usually, the temperature of the molten resin is preferably 260 to 340 ° C. Before applying the polyethylene composition of the present invention onto a paper substrate, it is preferable to subject the paper substrate to an activation treatment such as corona discharge treatment or flame treatment. It is also an effective method to subject the surface of the molten resin film, which is adhered to the paper substrate, to an oxidation treatment such as ozone treatment.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples unless the gist thereof is exceeded. The evaluation method is as follows. (1) Density Density was measured according to JIS K7112: 1999. (2) Melt mass flow rate According to JIS K7210: 1999, MFR (190
/2.16) was measured at a temperature of 190 ° C. and a load of 2.16 kg. MFR (190 / 21.6) is also JIS
K7210: 1999, temperature 190 ° C., load 21.
It was measured at 6 kg.

(3) FRR FRR was calculated from the above-mentioned measured value of MFR by the following formula. FRR = MFR (190 / 21.6) / MFR (190
/2.16) (4) Melt tension Melt tension (190 ° C MT) is measured at 190 ° C, 2.0
Using a nozzle capillary rheometer with mm diameter, 60
The tension was measured when polyethylene was extruded at mm / min and pulled at 2 mm / min. In addition, melt tension (240 ° C M
In T), similarly, a nozzle capillary rheometer having a measurement temperature of 240 ° C. and a diameter of 2.0 mm was used to measure the tension when polyethylene was extruded at 60 mm / min and pulled at 2 mm / min.

(5) Melt tension ratio (MTR) The melt tension ratio (MTR) was determined by the following equation from the above measured melt tension. MTR = (240 ° C. MT) / (190 ° C. MT) (6) High-speed processability As a measure of high-speed processability, the speed at which resin film breakage and surging occur was measured and comprehensively evaluated. The laminating process uses a 65 mm laminating machine, and the base material is 75 g.
/ Cm ² Kraft paper was used and the molding temperature was 320 ° C. The evaluation criteria for high-speed processing are: ◎: 500 m / min or more is possible, ◯: 400 m / min or more is possible, △: 3
Processing was possible at 00 m / min, x: less than 300 m / min.

(7) Neck-in Neck-in was carried out under the same conditions as the above-mentioned evaluation of high-speed workability. Die opening width 400 mm, laminating speed 200 m / min,
Molding was performed under the condition of an air gap of 130 mm, and the difference between the die opening width and the lateral length of the resin coated portion was measured. The evaluation standard of neck-in is that the total value of neck-in on both sides is ◎: within 20%, ◯: within 25%, Δ: within 35%, and ×: over 35% of the die width. (8) Heat resistance: 100 g / min at a processing speed of 75 g / cm ² Kraft paper coated with a 20 micron resin film 20 cm resin coated paper
The sample was cut out in four directions, and this sample was left in an oven at 130 ° C. for 90 seconds, and then the number of pinholes was measured. The criteria are ◎: 2 or less, ◯: 5 or less, Δ: 10 or less, ×: 1
Expressed as one or more.

(9) Amount of smoke generated A smoke component generated during processing is suction-collected by a suction duct at the upper part of the slit die attached to the extruder and quantified by a particle counter mounted at a position 5 m away from the suction part. Was done. The evaluation criteria are that the gas introduced into the particle counter contains 0.3 or more micron-sized smoke generating components, ◎: less than 10,000 / liter, ◯: 2
Less than 10,000 / liter, △: Less than 50,000 / liter, x:
Expressed as 50,000 pieces / liter or more. (10) The number of gels having a size of 0.1 mm or more in 1600 cm ^{2 of the} gel-melted resin film was evaluated. The evaluation standard is ◎: less than 5,
◯: Less than 10; Δ: less than 30; x: expressed as 30 or more. (11) Comprehensive judgment The lowest rank of the evaluations in the above (1) to (4) was taken as the rank of the comprehensive judgment.

[0026]

[Example 1] Density 918 kg / cm ³ , MFR 1.0 g
/ 10 minutes, melt tension ratio 0.97, FRR 48, 190 ° C.
High-density low-density polyethylene with a melt tension of 12.9
0 parts by weight, MFR 45 g / 10 minutes, density 966 kg / c
m ^3, the high-density polyethylene 90 parts by weight total value is 150ppm of each component of the carbon atoms 18 and 20 extracted with chloroform melt mixed by a single-screw extruder, at a resin temperature of the composition 320 ° C. Laminated. The physical properties of the high-pressure low-density polyethylene 1 and the high-density polyethylene A used in this example are shown in Tables 1 and 2. Table 3 shows the mixing ratio of the high-pressure low-density polyethylene and the high-density polyethylene used in this example. Table 4 shows the results of the workability evaluated using these resins.

[0027]

Examples 2 to 3 Instead of the combination of the high pressure low density polyethylene and the high density polyethylene used in Example 1, the high pressure low density polyethylene 1 and 2 shown in Table 1 were used.
The high-density polyethylenes A to B shown in Table 2 were used, and the compositions of the combinations shown in Table 3 were used to carry out lamination in the same manner as in Example 1, and the workability at that time was evaluated. Table 4 shows the respective evaluation results. From the results in Table 4, the high-pressure method low-density polyethylene resin component and the high-density polyethylene resin composition having the physical properties defined in the present invention are very good in high-speed laminating processing, and emit a small amount of smoke during processing. It can be seen that the physical properties of the product as a resin-coated paper are of excellent quality.

[0028]

Comparative Examples 1 to 3 In Comparative Examples 1 to 3, instead of the combination of the high pressure low density polyethylene and the high density polyethylene used in Example 1, various combinations of compositions shown in Table 3 were evaluated. Other than the above, the processability and the physical properties of the product were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 4. From the results of Table 4, in Comparative Examples 1 to 3 which do not satisfy the requirements of the present invention, good results cannot be obtained in any of the laminate processability and the physical properties of the resin-coated paper products. For example,
When the melt tension ratio of the high-pressure low-density polyethylene is less than 0.8 and the formula (2) of this patent is not satisfied (Comparative Example 1), high-speed processability and neck-in deteriorate. Also, MF
When R is less than 0.5 g / 10 minutes (Comparative Example 3), gel is generated and the product quality is deteriorated. Furthermore, when the total value of each component having 18 and 20 carbon atoms contained in the high-density polyethylene exceeds 400 ppm (Comparative Example 2), the amount of smoke generated during processing becomes extremely large.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

INDUSTRIAL APPLICABILITY The composition of the present invention has a very good high-speed molding processability of a resin layer in polyethylene resin-coated paper, and further suppresses smoke generation during processing, which enables stable production for a long period of time. In addition, it brings about a great effect that a resin-coated paper having excellent moisture resistance and heat resistance can be produced.

Claims (2)

[Claims] 1. A resin composition comprising a high-density polyethylene having a density of 950 kg / m ³ or more and a high-pressure low-density polyethylene, wherein the high-pressure low-density polyethylene has a melt mass flow rate of 0 at a density of 930 kg / m ³ or less. ．
5 to 3.0 g / 10 minutes, the melt tension ratio represented by the following formula (1) is 0.8 or more, and the relationship between FRR and melt tension satisfies the following formula (2) 5 to 40 parts by weight A polyethylene composition for resin-coated paper, characterized in that the high-density polyethylene is 95 to 60 parts by weight. MTR = (240 ° C. MT) / (190 ° C. MT) (1) (190 ° C. MT) ≧ 0.65 (FRR) −20 (2) where MTR in the equations (1) and (2) is the melt tension ratio. , MT is melt tension, and FRR is flow rate ratio. 2. The high-density polyethylene has a melt mass flow rate of 30 g / 10 minutes to 60 g / 10 minutes and a density of 96.
The polyethylene composition for resin-coated paper according to claim 1, wherein the total of each component having a carbon number of 18 and 20 when extracted with chloroform of 0 kg / m ³ or more is 400 ppm or less.