JPH04220340A - Manufacture of laminated item - Google Patents

Abstract

PURPOSE:To produce a polyethylene laminated item which has lamination moldability such as high speed moldability, thin thickness moldability, low neck-in property at a relatively low temperature and also adhesiveness to a base material and a weak smell. CONSTITUTION:A composition 1 comprising 30-90wt.% low density polyethylene having a melt flow rate of 1-20g/10min and the ratio of 0.55-0.90 between its limiting viscosity and that of straight chain polyethylene having the same weight-average molecular weight and 70-10wt.% low density polyester having a melt flow rate of 3-15g/10min and the ratio of 0.10-0.45 between its limiting viscosity and that of straight chain polyethylene having the same weight-average molecular weight, and an ethylene adhesive resin composition 11 are co-extruded and laminated.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a polyethylene laminate that achieves both high-speed moldability at relatively low temperatures, thin-wall moldability, low neck-in properties, and adhesion to base materials, and has low odor. Concerning product molding methods.

0002

BACKGROUND OF THE INVENTION Polyethylene has excellent heat-sealability and moisture-proofing properties, and is easily extruded, so it can be laminated onto various resin films, aluminum foils, papers, etc. to add these properties. Such laminate products are useful as various packaging materials and are used in large quantities.

[0003] For laminating polyethylene, extrusion lamination is often used. In this method, polyethylene is heated and melted using an extruder, extruded into a film, and then placed on a base material, and molding and bonding are performed simultaneously.

At this time, in order to obtain high-speed moldability and thin-wall moldability, there are measures such as using a resin with a high melt flow rate (hereinafter abbreviated as MFR) or increasing the molding temperature to increase the fluidity of the resin. It is being done.

[0005] Furthermore, since polyethylene is non-polar and difficult to adhere to polar substrates, it is possible to use an adhesive called an anchor coating agent, but in addition to the complicated coating process, it is difficult to adhere to polar substrates. There is also a method of applying electric discharge. However, in this case, it is necessary to separately prepare a special device, which is not preferable. An alternative method to these is to raise the molding temperature, but in this case, sufficient adhesion cannot be obtained unless the resin surface is oxidized to some extent, so it is necessary to raise the resin temperature compared to film molding etc. be.

For these reasons, low-density polyethylene is usually laminated at a high temperature of 300 to 330°C. As mentioned above, this is necessary to improve moldability and adhesion, but on the other hand, it can cause oxidative deterioration and decomposition of the resin due to high temperatures, resulting in a decrease in heat sealability (such as an increase in heat seal temperature and a decrease in heat seal strength). ), which causes problems such as deterioration of product physical properties and deterioration of product odor. There is also the problem that smoke generates oil droplets and roll stains, which contaminate the product. Moreover, the high temperature, smoke, odor, etc. during molding significantly deteriorate the working environment.

[0007] In the field of food packaging and the like, the increase in odor and low molecular weight components caused by oxidative deterioration of polyethylene poses a major problem. The simplest and most effective way to solve this problem is to lower the molding temperature as much as possible, but of course the problem is that moldability and adhesiveness deteriorate.

Among these, moldability at low temperatures can be solved by increasing the MFR of the resin as described above. When molding is performed at the low temperature (270 to 290°C), sufficient moldability can be obtained by using polyethylene with an MFR of about 20 g/10 minutes. However, increasing the MFR to such a high level has the disadvantage of reducing the strength of the resin and causing the resin to ooze out during heat sealing, and is not a general solution.

Regarding the improvement of adhesion during low temperature molding, methods include laminating once at high temperature and then laminating at low temperature a second time, coextrusion lamination method in which high temperature and low temperature resins are laminated at once, and resin released from a die. Methods such as ozone treatment, in which the surface is oxidized by spraying ozone on the surface of the material, and adhesive resins made by graft modification or copolymerization of monomers with polar groups, have been used.

[0010] Among these methods, the method of laminating twice requires two laminating equipment in the production line, which complicates the process and increases the thickness of the laminate. In addition, in coextrusion lamination with a temperature difference, the die-merging type cannot create a sufficient temperature difference. Although the die-outside merging type improves the direct negative effects on the product, such as deterioration and odor, it cannot solve the problems caused by smoke generation.

[0011] Ozone treatment can oxidize only the surfaces that require adhesion at low temperatures;
etc. are known. However, ozone has problems such as odor and corrosiveness, so its use is still limited.

[0012] Many adhesive resins are commercially available,
There are several resins that have excellent low-temperature adhesion properties, especially when adhering to aluminum foil. However, these adhesive resins generally have odor, inferior moldability, and are expensive compared to ordinary polyethylene. Although the odor and cost can be improved by using it in a coextrusion laminate, the moldability was not improved even in coextrusion using coextrusion in a die.

[0013] As described above, it is difficult to achieve both suppression of smoke generation and deterioration with moldability and adhesion using conventional techniques, and the current situation is that one or the other is sacrificed.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems associated with the prior art as described above. In other words, a method for manufacturing a polyethylene laminated product that achieves both high-speed moldability, thin-wall moldability, low neck-in properties, and other laminate moldability at relatively low temperatures, as well as adhesion to base materials, and has low odor and good heat sealability. The goal is to provide the following.

[0015]

[Means for Solving the Problems] As a result of various studies conducted by the present inventors in order to solve the above problems, the present inventors have developed a coextrusion lamination method in which a specific polyethylene composition and an adhesive resin are combined in a die. By adopting this method, it is possible to manufacture laminated products with excellent lamination formability and adhesion such as high-speed moldability, thin-wall moldability, and low neck-in properties at low temperatures of 280°C or lower, as well as good heat-sealing properties with little odor. I found out.

That is, (1) MFR is 1 to 20 g/10
It consists of 30-90% by weight of low-density polyethylene (A) with an MFR of 3-15g/10min and 70-10% by weight of low-density polyethylene (B) with an MFR of 3-15g/10min.
g/10 min of low density polyethylene composition (l),
(i) The ratio Gη (= [η ]A/
[η] LA) is 0.55 to 0.90, and (ii) (
Ratio of the intrinsic viscosity [η]B of B) to the intrinsic viscosity [η]LB of a linear polyethylene whose weight average molecular weight determined by a light scattering method is the same as that of (B) Gη(=[η]B/[ η〕
A low density polyethylene composition (l) characterized in that LB) is 0.10 to 0.45, and an ethylene adhesive resin composition (ll) containing 0.05 to 5% by weight of carboxyl groups or derivatives thereof. ) was found to be able to be solved by coextrusion laminating using a coextrusion T die so that the composition (ll) was in contact with the base material on at least one side of the base material, and the present invention was achieved based on this discovery.

The present invention will be explained in detail below. The low-density polyethylene (A) and low-density polyethylene (B) constituting the low-density polyethylene composition (l) used in the production method of the present invention are so-called high-pressure polyethylene.

Low-density polyethylene (hereinafter sometimes referred to as LDPE) obtained by polymerization in the presence of a free radical generator such as peroxide at a high pressure of 1000 to 3500 atmospheres can be polymerized by Ziegler polymerization at a low pressure of several tens of atmospheres. Unlike polyethylene (hereinafter sometimes referred to as HDPE) or a copolymer of ethylene and α-olefin (hereinafter sometimes referred to as L-LDPE) obtained by coordination anion polymerization using a catalyst, It is known that long chain branches exist. The presence of these long chain branches in LDPE has an effect on its viscoelasticity during melting, compared to HDPE and L-LDP without long chain branches.
It is known that it exhibits significantly different properties compared to E, especially elastic properties. That is, it is also known that LDPE has excellent film formation stability during inflation molding and excellent neck-in characteristics during laminate molding. However, it is known that L-LDPE is superior in terms of stretchability.

[0019] LDPE is generally produced in an autoclave or a tubular reactor, but the LDPE obtained using either reactor has long chain branches. The degree of long chain branching varies depending on the pressure and temperature during polymerization.

Unlike short chain branches, the number and length of long chain branches cannot be accurately quantified using 13C-NMR. The degree or index of long chain branching is determined by the ratio of the intrinsic viscosity of low-density polyethylene with long chain branches of the same molecular weight and linear polyethylene with few long chain branches, Gη (= [η ]B/[η]L). Here, [η]B is the intrinsic viscosity of low-density polyethylene with long-chain branches, and [η]L is a straight line with the same molecular weight as the low-density polyethylene with long-chain branches (both molecular weights determined by the light scattering method above). This is the intrinsic viscosity of chain polyethylene.

In addition, the intrinsic viscosity [η]B, [η]L is the viscosity measured with a dilute solution of tetralin at 130°C,
Viscosity at the point where the concentration is pushed outward to zero (ηSP/C)C →0
It is expressed as

The present inventors focused on the long chain branching index and MFR, and conducted trial production under various conditions to improve high-speed moldability at low temperatures,
A detailed study of thin-wall moldability, heat sealability, hot tack properties, and neck-in properties revealed that low-density polyethylene with an intrinsic viscosity ratio Gη of 0.55 to 0.90:
It was found that even if the MFR is smaller than the usual laminate grade of about 1 to 3 g/10 minutes, it is excellent in high-speed moldability at low temperatures and thin-wall moldability, but slightly inferior in neck-in properties. On the other hand, when the ratio Gη of the limiting viscosity is 0.15 to 0.45, low-temperature and high-speed formability is poor when the MFR is 11 g/10 minutes or less, and high-speed formability of 250 m/min or more is poor at a low temperature of 280°C or less. In order to obtain this, an MFR of 15 g/10 minutes or more was required. However, when the MFR is 15 g/10 minutes or more, low-temperature and high-speed moldability can be obtained, but the neck-in is large and the heat seal strength and hot tack properties are poor.

As a result of studying how to take advantage of the advantageous characteristics of both low density polyethylenes by combining these low density polyethylenes with significantly different intrinsic viscosity ratios Gη, we found that (1) MF
R is 1 to 20 g/10 minutes, and low density polyethylene (
Low density polyethylene composition (l) having an MFR of 2 to 10 g/10 min, consisting of A) 30 to 90 wt% and (B) 70 to 10 wt% low density polyethylene having an MFR of 3 to 15 g/10 min. So, (i) the intrinsic viscosity of (A) [η]A
The ratio Gη (= [η] A / [η] LA) of linear polyethylene whose weight average molecular weight determined by a light scattering method is the same as that of (A) [η] LA is 0.55 to 0.
90, and (ii) the ratio Gη of the intrinsic viscosity [η]B of (B) and the intrinsic viscosity [η]LB of a linear polyethylene whose weight average molecular weight determined by a light scattering method is the same as that of (B). (
= [η]B / [η]LB) of 0.10 to 0.45, the composition (l) can be molded at a high speed of 200 m/min or more at a low temperature of 280°C or less. However, it has been found that it has excellent formability in thin walls of 10 to 15 μm, and excellent heat seal strength, hot tack properties, and neck-in properties.

The ratio Gη of the intrinsic viscosity of the low density polyethylene (A) used in the present invention is 0.55 to 0.9.
0, more preferably 0.65 to 0.90. The ratio Gη of the intrinsic viscosity of the low density polyethylene (A) is 0.
If it is less than 55, it is not preferable because low-temperature and high-speed moldability is poor. The ratio Gη of the intrinsic viscosity of low density polyethylene (A) is
Although the upper limit is not particularly limited, it is practically difficult to obtain a value exceeding 0.90 using the high-pressure method.

MFR of low density polyethylene (A) is 1
~20g/10 minutes, preferably 3.5~15g/
It's 10 minutes. MFR of low density polyethylene (A) is 1
If the MFR is less than 20 g/10 minutes, low-temperature, high-speed moldability and thin-wall moldability will be poor, and if the MFR exceeds 20 g/10 minutes, it will be difficult to balance heat seal strength and neck-in properties.

Further, the ratio Gη of the intrinsic viscosity of the low density polyethylene (B) used in the present invention is 0.10 to 0.
．． 45, preferably 0.15 to 0.35. Low density polyethylene (B) having an intrinsic viscosity ratio Gη of less than 0.10 is substantially difficult to manufacture. Moreover, if the ratio Gη of the limiting viscosity exceeds 0.45, the neck-in characteristic will be poor.

MFR of low density polyethylene (B) is 3
~15g/10min, preferably 4~12g/10
It's a minute. MFR of low density polyethylene (B) is 3g/
If the time is less than 10 minutes, there is a drawback that low-temperature, high-speed moldability and thin-wall moldability are poor. Furthermore, when the MFR of the low density polyethylene (B) exceeds 15 g/10 minutes, the low-temperature, high-speed moldability is extremely good, but the neck-in properties are poor.

The method for producing low density polyethylene (A) and low density polyethylene (B) may be either an autoclave method or a tubular method.

[0029] The mixing ratio (weight) of low density polyethylene (A) and low density polyethylene (B) is 30:70 to 90:1.
0, preferably 50:50 to 80:20. If the value of low-density polyethylene (A) is less than 30, low-temperature, high-speed moldability and thin-wall moldability will be poor; if it exceeds 90,
A fully satisfactory neck-in characteristic cannot be obtained.

[0030] The low density polyethylene (A) and low density polyethylene (B) are mixed by mixing and kneading them in a molten state using a conventional extruder or kneader under conventional conditions.

The MFR of the low density polyethylene composition (l) obtained as described above is 2 to 10 g/10 minutes, preferably 3 to 9.5 g/10 minutes. If the MFR of the low-density polyethylene composition (l) is less than 2 to 10 g/10 minutes, low-temperature, high-speed moldability and thin-wall moldability cannot be sufficiently satisfied;
When the MFR exceeds 10 g/10 minutes, heat seal strength and hot tack properties are insufficient.

Next, the ethylene adhesive resin composition (11) used in the production method of the present invention will be explained. In the present invention, the ethylene adhesive resin composition (ll) is an ethylene polymer containing a carboxyl group or a derivative thereof, such as an acid anhydride group, in the molecule.

[0033] The ethylene polymer mentioned here includes a homopolymer of ethylene, a copolymer of ethylene and other monomers,
Furthermore, it refers to those containing mixtures of these.

Examples of the carboxylic acid mentioned here include acrylic acid, methacrylic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, and 5-norbornene-2,3-dicarboxylic acid. Further, as carboxylic acid derivatives, cyclic ones are preferable, specifically maleic anhydride,
Examples include itaconic anhydride, citraconic anhydride, and dodecenylsuccinic anhydride. In some cases, two or more of these may be used in combination.

Methods for introducing a carboxyl group or a derivative thereof into the molecule of an ethylene polymer include a method of copolymerizing a radically polymerizable carboxylic acid or a derivative thereof during polymerization of ethylene using a high-pressure method; There are methods such as graft copolymerization of a radically polymerizable carboxylic acid or a derivative thereof using a radical initiator such as an organic peroxide, and ethylene adhesive resins made by these methods. Any of the compositions (ll) can be suitably used in the present invention. The content of carboxylic acid or its derivative is determined by the amount of carboxylic acid or its derivative in the ethylene adhesive resin composition (l
0.05 to 5% by weight in l). If it is less than 0.05% by weight, the adhesive effect is insufficient, and if it exceeds 5% by weight, the adhesive effect remains unchanged. Alternatively, it may be a multicomponent copolymer consisting of three or more components in which ethylene is copolymerized with another comonomer in addition to carboxylic acid or its derivative. Furthermore, these ethylene adhesive resin compositions (11) can be used in combination with other resins as long as adhesiveness can be maintained.

Low density polyethylene composition (l) and ethylene adhesive resin composition (ll) used in the present invention
) may contain stabilizers, lubricants, antistatic agents, pigments, fillers and other additives as necessary. Next, a method for manufacturing a laminate according to the present invention will be explained.

The laminating base material used in the present invention mainly includes resin films or sheets such as polypropylene, polyamide, polyester, saponified ethylene-vinyl acetate copolymer, polyvinylidene chloride, aluminum, iron, copper, etc. Metal foils or metal plates such as alloys, cellophane, paper, cloth, nonwoven fabrics, etc., are used as components, and the surfaces of these base materials may be subjected to corona treatment, frame treatment, etc., as necessary.

In the method for producing a laminate of the present invention, a low density polyethylene composition (l) is applied to one or both sides of the base material.
) and the ethylene adhesive resin composition (ll) are coextruded and laminated into two layers. At this time, it is necessary that the ethylene adhesive resin composition (ll) be laminated on the base material side and the low density polyethylene composition (l) be laminated on the outer surface side. In the opposite configuration, the moldability is maintained, but the adhesiveness is decreased and the odor is worsened, so that the characteristics of the present invention cannot be exhibited.

As an apparatus for coextrusion lamination processing, it is preferable to use a coextrusion T die in which the materials are merged within the die or in front of the die. This is to improve moldability, and the coextrusion T die with confluence outside the die has little improvement effect.

[0040] The temperature during coextrusion lamination is 280°C.
The following are preferred. This is because smoke generation during molding increases rapidly when the temperature exceeds 280°C.

[0041]

[Examples] The present invention will be explained in more detail below with reference to Examples and Comparative Examples. In addition, each physical property value of an Example and a comparative example was measured according to the following method.

(1) Drawdown (DD) extruder:
φ90mm (50rpm), φ65mm (65rpm)
) Coextrusion, T-die width set to 750 mm, maximum molding speed at which the laminate layer can be stably molded without film breakage.

(2) Neck-in (NI) extruder: φ90
mm (50 rpm), φ65 mm (65 rpm) coextrusion, T die width set to 750 mm, molding speed 130 m
The amount by which the laminate width decreases when /min. However, the DD property is 130m.
If the speed does not reach /min, neck-in is performed at the DD speed.

(3) Adhesive strength Extruder: φ90mm (50rpm), φ65mm (6
5rpm) Coextrusion or φ90mm single layer with the same thickness, set the T die width to 750mm, and molding speed 13
The laminated sample was peeled off at the interface between the aluminum foil and the laminated film at 0 m/min, the sample width was 15 mm, and the peeling speed was 300 m.
The adhesive strength was defined as the peel strength at 180 degrees peeling at m/min.

Example 1 (Production of low density polyethylene (A)) Ethylene was polymerized in a 10 liter autoclave equipped with a stirrer under a pressure of 1200 kg/cm2 at an average polymerization temperature of 210°C. The MFR of the obtained low density polyethylene was 7.3 g/10 min.
The density was 0.920 g/cm3, and the ratio of intrinsic viscosity Gη was 0.68.

(Production of low-density polyethylene (B)) In the autoclave used in the production of low-density polyethylene (A), the average polymerization temperature was 26 at a pressure of 1650 kg/cm2.
Ethylene was polymerized at 0°C. The MFR of the obtained low density polyethylene was 7.0 g/10 min, and the density was 0.917 g/10 min.
cm3, and the ratio Gη of the intrinsic viscosity was 0.21.

(Preparation of low density polyethylene composition (l)) Low density polyethylene (A) and low density polyethylene (B)
) were mixed in a 30φ extruder at a mixing ratio of 70:30,
A low density polyethylene composition (l) was obtained. The MFR of the obtained low density polyethylene composition (l) is 7.3 g/10
The density was 0.919 g/cm3.

(Production of ethylene-based adhesive resin composition (11)) A copolymer of ethylene and maleic anhydride was produced using a high-pressure polyethylene production facility equipped with an autoclave-type reactor. Polymerization pressure is 1850kg/cm
2. The polymerization temperature was 200°C. After the polymer passed through the reactor, unreacted monomers were separated using a high-pressure separator and a low-pressure separator, and the polymer was pelletized using extrusion granulation equipment. The obtained copolymer had an MFR (190° C.) of 8.6 and a unit content derived from maleic anhydride of 2.2% by weight. Note that the copolymer composition was determined by infrared absorption spectrum. The copolymer had an MFR (190°C) of 7.0 and a density of 0.9165 g.
/cm3 of low density polyethylene at a polymerization ratio of 20/80. For mixing, both were dry blended in a tumbler, and then melted and kneaded at 170° C. using a 50 mmφ single screw extruder to form pellets. The MFR (190°C) of the mixture was 7.3 g/10 min, and the unit derived from maleic anhydride was 0.43% by weight.

(Lamination processing) The laminate molding machine is
A coextrusion laminate molding machine was used, which was equipped with a φ90 mm extruder and a φ65 mm extruder, and had a pre-die merging type in which the respective resins were merged in a feed block, then introduced into a T-die, and extruded as a two-layer molten film. A φ90 mm extruder was used for the low density polyethylene composition (l), and a φ65 mm extruder was used for the ethylene adhesive resin composition (ll), so that the ethylene adhesive resin composition (ll) was on the base material side. A coextrusion laminate of two seed layers was performed. The molding conditions at this time were a screw rotation speed of 50 rpm for a φ90 mm extruder.
, φ65 mm extruder was 65 rpm, die slit width was 0.7 mm, die width was 750 mm, die lip heaters were 2 x 5A, resin temperature directly under the die was 279°C, and the base material was PET prepared in advance. A laminate film with a three-layer structure of /low density polyethylene/aluminum foil was used and laminated on the aluminum foil side.

Evaluations were made at this time: drawdown property (maximum speed at which stable molding is possible), neck-in (decreased amount of laminate width), adhesive strength (aluminum foil and ethylene adhesive resin composition (II)
) and smoke generation during molding were evaluated. The resin and molding conditions are shown in Table 1, and the evaluation results are shown in Table 2.

Example 2 As shown in Table 1, the same low density polyethylene (
For A), MFR is 12.0 and density is 0.917g/
cm3 and a low density polyethylene (B) having an intrinsic viscosity ratio Gη of 0.23, but lamination molding was carried out in the same manner as in Example 1. The evaluation results are shown in Table 2.

Comparative Example 1 As shown in Table 1, the same low density polyethylene composition (l) as in Example 1 was used, and an ethylene adhesive resin composition (ll) was used.
) was used for single-layer extrusion lamination. The evaluation results are shown in Table 2.

Comparative Examples 2 and 3 As shown in Table 1, low density polyethylene (B) with MFR = 7.9 and Gη = 0.35 was used, and the ethylene adhesive resin composition (ll) was not used. Extrusion lamination of the layers was performed. The evaluation results are shown in Table 2.

Comparative Example 4 As shown in Table 1, low density polyethylene (A) was not used,
Laminate molding was carried out in the same manner as in Example 1 except that low density polyethylene (B) with MFR=7.9 and Gη=0.35 was used. The evaluation results are shown in Table 2.

Comparative Example 5 As shown in Table 1, the same ethylene adhesive resin composition (l) as in Example 1 was used without using the low density polyethylene composition (l).
Monolayer extrusion lamination was carried out using only 1). The evaluation results are shown in Table 2.

Comparative Example 6 Laminate molding was carried out in the same manner as in Example 1, except that low density polyethylene (B) with MFR=22.7 and Gη=0.23 was used as shown in Table 1. The evaluation results are shown in Table 2.

Comparative Example 7 Laminate molding was carried out in the same manner as in Example 1, except that low density polyethylene (B) with MFR=5.0 and Gη=0.71 was used as shown in Table 1. The evaluation results are shown in Table 2.

As shown in Table 1, low density polyethylene (A
) and low density polyethylene (B) was 20:80, but laminate molding was carried out in the same manner as in Example 1. The evaluation results are shown in Table 2.

[0059]

[Table 1]

[0060]

[0061]

[Effects of the invention] Polyethylene-based polyethylene that achieves both high-speed moldability at relatively low temperatures, thin-wall moldability, low neck-in properties, and other laminate moldability and adhesion to base materials, and has low odor and good heat sealability. A method for manufacturing a laminated product has been obtained.

Claims (1)

[Claims] [Claim 1] Melt flow rate is 1 to 20 g/1
0 minutes low density polyethylene (A) 30-90% by weight
and 70 to 10% by weight of low density polyethylene (B) having a melt flow rate of 3 to 15 g/10 minutes, and in a low density polyethylene composition (l) having a melt flow rate of 2 to 10 g/10 minutes. , (i) The ratio Gη(=[ η〕A / [η〕LA)
is from 0.55 to 0.90, and (ii) the intrinsic viscosity [η]B of (B) and the weight average molecular weight determined by a light scattering method are the same as those of (B) [ η
] LB ratio Gη (= [η] A / [η] LB) is 0.
10 to 0.45, and an ethylene adhesive resin composition (ll) containing 0.05 to 5% by weight of carboxyl groups or derivatives thereof are coextruded. A method for producing a laminate, which comprises coextrusion laminating using a T-die so that the composition (11) is in contact with at least one side of the base material.