JP3370754B2 - Polyethylene composition for lamination - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyethylene composition for laminating which has excellent adhesion to a substrate at a relatively low temperature in laminating molding, has a small odor of a molded article, and has laminating moldability such as low neck-in property. Regarding

[0002]

2. Description of the Related Art Polyethylene is excellent in heat-sealing property and moisture-proof property and can be easily extruded. Therefore, it can be laminated on various resin films, aluminum foil, paper and the like to add these properties. Such laminated products are effective as various packaging materials and are used in large quantities.

There are dry laminating method, wet laminating method and the like for laminating polyethylene, but extrusion laminating method is often used. This is one in which polyethylene is heated and melted using an extruder and extruded in a film shape is laminated on a substrate, and molding and laminating are simultaneously performed. For resins used in extrusion lamination,
In addition to the adhesiveness to the substrate, it is required that the odor of the molded product is small, high-speed moldability for improving productivity, thin-wall moldability, and less loss due to neck-in.

In order to obtain high-speed moldability and thin-wall moldability, a resin having a high melt flow rate (hereinafter abbreviated as MFR) is used, or a means for raising the molding temperature to increase the fluidity of the resin is used. .

On the other hand, polyethylene is non-polar and does not easily adhere to a polar base material. Therefore, by molding at a high temperature of 300 ° C. or higher to oxidize the polyethylene surface and introduce polar functional groups. The method of improving the adhesiveness with a base material is used. In addition to this, a method using an adhesive called an anchor coating agent can be used,
Also in this case, strong adhesion cannot be obtained unless the polyethylene itself has a certain degree of polarity. It is considered that this is because there is an affinity between polyethylene and the adhesive agent, and a chemical reaction, a hydrogen bond, or other interaction occurs between them.

For these reasons, low-density polyethylene is usually laminated at a high temperature of 300 to 345 ° C. This is necessary for improving moldability and adhesiveness as described above, but on the other hand, it causes oxidative deterioration and decomposition of the resin due to high temperature, resulting in deterioration of heat sealability (increased heat seal temperature, heat seal strength). It causes problems such as deterioration of physical properties of the product such as deterioration) and deterioration of odor of the product. In addition, there is a problem that oil droplets are generated due to smoke generation and roll contamination is caused, and these contaminate the product. Furthermore, the high temperature, smoke, odor and the like during molding significantly deteriorate the working environment.

In the fields of food packaging and the like, an increase in odor and low molecular weight components due to the oxidative deterioration of polyethylene is a serious problem. The simplest and most effective way to solve this problem is to lower the molding temperature, but naturally, the problem is that the moldability and adhesiveness deteriorate.

Among these problems, the low temperature molding can be solved by increasing the MFR of the resin as described above. When molding at a low temperature (250 ° C. to 290 ° C.), sufficient moldability can be obtained by using polyethylene having an MFR of about 20 g / 10 minutes. However, increasing the MFR in this way is not a practical solution because it has the drawback of increasing the neck-in at the time of molding, lowering the strength of the resin, and causing the resin to squeeze out during heat sealing.

Further, regarding the improvement of adhesion at the time of low temperature molding, a method of laminating once at a high temperature and then a low temperature for the second time, a coextrusion laminating method of laminating a high temperature resin and a low temperature resin at once, and a die were used. An ozone treatment method or the like in which ozone is sprayed on a resin to oxidize its surface is used. Of these, the method of laminating twice requires two laminating facilities in the production line, which complicates the process,
There are drawbacks such as an increase in the thickness of the laminate. Further, in a coextrusion laminate having a temperature difference, the confluence type in the die cannot make a sufficient temperature difference. In the case of the combined die outside die, direct adverse effects on the product, that is, deterioration, odor, etc. are improved, but the problem caused by smoking cannot be solved. Ozone treatment can oxidize only the surface requiring adhesion at low temperature, and it is also described in JP-A-57-157724. However, ozone has problems such as odor and corrosiveness,
Its use is still limited. As described above, it is difficult for the conventional technology to suppress both smoke generation and deterioration and formability and adhesiveness at the same time, and at present, one of them is sacrificed.

[0010]

As described above, it has been difficult with the conventional techniques to suppress smoke generation and deterioration and to achieve both moldability and adhesiveness. It is an object of the present invention to provide a polyethylene composition which has excellent adhesiveness to a substrate at a relatively low temperature in laminate molding, has little odor of a molded article, and has laminate moldability such as low neck-in property. .

[0011]

Means for Solving the Problems As a result of studies to solve the above problems, the present inventors have found that the problem can be solved by blending low density polyethylene and an oligomer having a specific functional group. The present invention has been completed. That is, in the present invention, (A) melt flow rate is 1 to 20 g /
70-98% by weight of low-density polyethylene of 10 minutes, and (B) oligomer 30-2 having a functional group at the end
A polyethylene composition for laminating comprising 10% by weight is provided. Hereinafter, the present invention will be described in detail.

The low-density polyethylene (hereinafter referred to as LDPE) which is the component (A) used in the present invention is a so-called high-pressure polyethylene, which is present under a high pressure of 1000 to 3500 atm in the presence of a free radical generator such as peroxide. Obtained by polymerizing. The reactor used for the polymerization may be either an autoclave or a tubular type.
LDPE produced by such a method is different from an ethylene homopolymer or a copolymer of ethylene and α-olefin (hereinafter referred to as LLDPE) polymerized at a low pressure of several tens of atm using a Ziegler catalyst, etc. It is known to have branches. It is known that the presence of this long-chain branch exhibits relatively high elasticity when melted, and therefore has excellent neck-in characteristics during laminate molding. In the present invention, such LDPE is preferably used.

LDPE MFR (JIS K7210)
Is 1 to 20 g / 10 minutes, preferably 3 to 15 g /
10 minutes. When the MFR is less than 1 g / 10 minutes, the high-speed moldability at low temperature and the thin-wall moldability are poor, and the MFR is 20 g /
When it exceeds 10 minutes, it is difficult to balance the heat seal strength and the neck-in characteristics, which is not preferable.

The oligomer having a functional group at the terminal which is the component (B) in the present invention is an oligomer having a functional group at at least one terminal in one molecule which is a liquid rubber or a waxy solid.

Here, the functional group is a hydroxy group, an amino group, a carboxyl group or an epoxy group. Two or more kinds of the oligomers having these functional groups at the ends may be used in combination as long as the purpose is not impaired.

The number average molecular weight of the oligomer having a terminal functional group is 800 to 15,000, preferably 1,000 to 1
It is 2,000, more preferably 1200 to 10,000. When the number average molecular weight is less than 800, smoke is generated during laminate molding and odor remains on the product, which is not preferable. Further, when the number average molecular weight exceeds 15,000, no improvement is seen in the adhesiveness to the substrate during low temperature molding.

Specific examples of the oligomer having a terminal functional group in the present invention include polybutadiene, polyisoprene, isobutylene-isoprene copolymer, polybutene, butadiene-acrylonitrile copolymer, styrene-butadiene copolymer, petroleum resin. Further, it is an oligomer which is obtained by partially or completely hydrogenating these and which has a functional group at least at one end in one molecule.

These oligomers are polymerizable monomers such as 1,3-butadiene and 1,3 as long as the performance of the polyethylene composition for lamination of the present invention is not impaired.
3-pentadiene, isoprene, chloroprene, 2,3
-Dimethyl-1,3-butadiene, 1-phenyl-1,
3-butadiene, piperylene, 2-methylbutene-1,
2-methylbutene-2, styrene, vinyltoluene, α
-Methylstyrene, indene and the like may be copolymerized. Further, these copolymers may be partially or completely hydrogenated.

The oligomer having a functional group at these terminals can be produced by a known method. Commercially available products thereof include hydroxy-terminated hydrogenated 1,4-polybutadiene (“Polytail H” and “Polytail HA” manufactured by Mitsubishi Kasei Co., Ltd.) and hydroxy-terminated hydrogenated polyolefin (“Epol” manufactured by Idemitsu Petrochemical Co., Ltd.). ), Hydroxy-terminated hydrogenated 1,2-polybutadiene (“NISO-PBG-1000” manufactured by Nippon Soda Co., Ltd., “NIS”)
SO-PB GI-1000 "), amino-terminated acrylonitrile-butadiene rubber (" Hyc "manufactured by Ube Industries, Ltd.)
ar-ATNB ") and the like are easily available and can be preferably used.

LDPE which is the component (A) in the present invention
The compounding ratio of 70 to 98% by weight, preferably 75 to 95
% By weight. If it is less than 70% by weight, neck-in becomes large, and if it exceeds 98% by weight, the adhesiveness becomes insufficient, which is not preferable.

In order to obtain the polyethylene composition for lamination of the present invention, the above-mentioned respective components are mixed by a conventionally known method, for example, an open roll, a Banbury mixer, a kneader,
A kneading method using an extruder or the like may be appropriately used. The kneading temperature is usually 140 ° C to 350 ° C, preferably 170 ° C to 300 ° C.

Further, the polyethylene composition for lamination of the present invention may optionally contain a conventional additive such as a plasticizer.
Lubricants, various stabilizers, antiblocking agents, antistatic agents,
Dyes, pigments, various fillers, etc. may be added.

The polyethylene composition for laminating of the present invention can be laminated on various substrates by an extrusion laminating method. The base material in the present invention includes, in addition to polyolefins such as polyethylene and polypropylene that are generally used for laminating, plastic films such as polyamide and polyester, and those obtained by vapor-depositing a metal such as aluminum on these plastic films, and paper. , Aluminum foil, etc.

When the polyethylene composition is laminated on these substrates by the extrusion laminating method, the molding temperature is generally 2
It is in the range of 40 to 345 ° C. At a molding temperature higher than 345 ° C, neck-in during molding becomes large and smoke is also increased. In addition, heat seal strength is deteriorated due to oxidative deterioration, and odor of the product is deteriorated. Molding temperature is preferably 260
By setting it to ~ 300 ° C, the neck-in is small,
It is possible to obtain a laminated product which has less smoke during molding, has excellent heat-sealing strength, has less odor, and has excellent adhesiveness. The obtained laminated product is used as a packaging material and processed paper.

[0025]

EXAMPLES The present invention will be described in more detail 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) Neck-in extruder: φ90 mm (50 rpm), T-die width 750
It was evaluated by the reduction amount (mm) of the laminate width when the molding speed was set to 130 mm / min at a predetermined temperature. (2) Adhesive strength extruder: φ90 mm (50 rpm), T die width 750
mm was set, and aluminum foil or polyamide film was used as the base material, and laminate molding was performed at a predetermined temperature at a molding speed of 130 mm / min to obtain a sample. The laminate sample was peeled off at the interface between the aluminum foil or nylon film and the laminate film, and the peel strength at 150 mm peeling at a sample width of 15 mm, peeling speed of 300 mm / min was taken as the adhesive strength. (3) Smoke state MFR 1.5g / 10min, density L 0.920g / cm ³
When the DPE was molded at 310 ° C., the state of smoke was rated as ◯, when there was more smoke than that, it was rated as ×, and when less smoke was rated as ⊚, the evaluation was carried out in three levels.

The following two types of LDPE were used as the component (A). LD4: MFR 4.0 g / 10 minutes, density 0.921 g /
cm ³ (Brand: Mitsubishi Polyethylene-LD LK40 Mitsubishi Yuka
Co., Ltd.) LD14: MFR13.7g / 10 minutes, density 0.919
g / cm ³ (Brand: Petrosene 212 manufactured by Tosoh Corporation) (B) As the oligomer having a functional group at the terminal, the following was used. FO1: hydrogenation amount 80% of terminal hydroxylated 1,4-polybutadiene (1,4-bond), number average molecular weight 280
0, average hydroxy number 2.3 / molecule (brand name: Polytail H Mitsubishi Kasei Co., Ltd.) FO2: Aminated butadiene-nitrile rubber at both ends (acrylonitrile content 16.5%, number average molecular weight 4)
000, amino group equivalent 900) (Brand name: Hycar-ATNB, Ube Industries, Ltd.)

(Examples 1 to 7) LDPE (A) whose type and blending amount are shown in Table 1 and oligomer (B) having a functional group at the end were mixed for 5 minutes using a Henschel mixer, and then vented. It was melt-kneaded at a temperature of 240 ° C. and pelletized by an attached extruder. A sample was obtained from each of the obtained pellets by using a laminating machine using the temperature and the substrate shown in Table 1 of the machine. As shown in Table 1, the evaluation results were that they all had excellent adhesive strength, as well as smoke emission and neck-in.

Comparative Examples 1 and 2 In Example 4,
The ratio of the component (A) and the component (B) was changed, but the adhesive strength or smoke was poor.

[0030]

[Table 1]

[0031]

EFFECT OF THE INVENTION A polyethylene composition for laminating is obtained which has both a good laminating moldability such as a low neck-in property and a high adhesiveness to a substrate and which emits less smoke during molding.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Ippei Kagaya, 3-2 Chidori-cho, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Showa Denko K.K. No. 2 Showa Denko KK Kawasaki Plastics Research Laboratory (56) Reference JP-A-58-67738 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08L 23 / 04-23 / 08

Claims (2)

(57) [Claims] 1. A melt flow rate of (A) is 1 to 20 g.
70-98% by weight of low density polyethylene which is / 10 minutes,
And (B) an oligomer 30 having a functional group at the terminal
A polyethylene composition for lamination comprising 2% by weight. 2. The functional group of the oligomer (B) having a functional group at the terminal is one group selected from a hydroxy group, an amino group, a carboxyl group and an epoxy group. Polyethylene composition for laminating.