JPH01222920A - Method for manufacturing co-extruded laminate article - Google Patents

Abstract

PURPOSE:To enable a co-extruded laminate article with an excellent surface luster, anti-blocking, heat-proof and curl-proof by performing a melt co-extruded laminate on one side of a basement for the high density polyethylene having specified density and low density polyethylene having specified swell ratio wherein the thickness ratio of the layer comprising the high density polyethylene is predetermined and the layer comprising the low density polyethylene is used as an adhesive surface to the basement. CONSTITUTION:On one side of the basement, the melt co-extruded laminate is performed for the high density polyethylene 1 of the density 0.940-0.970g/cm<2>, high-load melt flow rate/melt flow rate 20-40 and the low density polyethylene 2 of the density 0.910-0.935g/cm<2>, swell ratio 50% or more wherein the rate of film thickness of the layer comprising the high density polyethylene 1 is 10-50% of the total film thickness of both resin and the layer comprising the low density polyethylene 2 is used as the adhesive surface to the basement 3. As the basement 3, films such as polyethylene, fabric, non-woven fabric, metal foil or metal plate such as aluminum, besides paper such as craft paper are used.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for producing a coextrusion laminate, and in particular to a method for producing a coextrusion laminated paper having excellent surface gloss, blocking resistance, heat resistance, and curl resistance. The present invention relates to a method for producing a coextrusion laminate suitable for producing a coextrusion laminate.

[Conventional technology] Art coat, vinyl coat, and high-pressure low-density polyethylene laminate have been conventionally used to impart water resistance, moisture resistance, coatability, and cosmetic properties to paper base materials such as paperboard, high-quality paper, and kraft paper. Surface modification methods such as Among these, polyethylene laminated paper, in which a thin film of high-pressure low-density polyethylene is formed on the surface of a paper base material, has excellent surface properties and productivity, so it is used in packaging cartons, silicone-coated release paper, and waterproof paper. It is used in large quantities in various processed paper fields such as liners for corrugated cardboard.

However, with polyethylene laminated paper using conventional high-pressure low-density polyethylene, the surface gloss for giving cosmetics to packaging cartons and water-resistant cardboard, and the supply of cut plates to printing and punching processes for packaging cartons, The blocking resistance of packaging cartons, the heat resistance during press varnish coating of packaging cartons and the silicone coating of release paper, and the curl resistance of release paper are insufficient.

[Problems to be Solved by the Invention] The purpose of the present invention is to overcome the drawbacks of the conventional high-pressure low-density polyethylene laminates, especially high-pressure low-density polyethylene laminated paper, and improve surface gloss, blocking resistance, and heat resistance. Another object of the present invention is to provide a method for producing a coextrusion laminate having excellent curl resistance.

[Means for Solving the Problems] The present invention provides a method for producing a coextrusion laminate that can achieve the above objects.

That is, the present invention uses high-density polyethylene with a density of 0.940 to Q, 970 t/ca, and a high load melt flow rate/melt flow rate of 20 to 40 on one side, and a low density polyethylene on one side. 910-0.935 g/
crA, low density polyethylene with a swell ratio of 50% or more, the ratio of the film thickness of the layer made of high density polyethylene is 10 to 50% of the total film thickness of both the above resins, and the layer made of low density polyethylene. The present invention relates to a method for producing a coextrusion laminate, which is characterized by performing melt coextrusion lamination as an adhesive surface to a base material.

The method for producing a coextrusion laminate of the present invention will be described below.

(A) Base material In addition to paper such as paperboard, high-quality paper, and kraft paper, base materials used in the present invention include films such as cellophane, polyamide, polyester, and polyethylene, woven fabrics, nonwoven fabrics, wood, and metals such as aluminum and iron. Foil, metal plate, etc. are used.

(B) High-density polyethylene The density of the high-density polyethylene used in the present invention is 0.940 to 0.970 g/c+a, particularly preferably 0.945 to 0.9135 g/ca.

High-density polyethylene having a density of less than 0.940 g/c+M is not preferred because the resulting coextruded laminate will have insufficient heat resistance and blocking resistance. Moreover, high-density polyethylene with a density exceeding 0.970 g/cIa is difficult to manufacture.

Next, high-density polyethylene melt flow rate used in the present invention (according to JIS K 7210)
The MFR (measured at 190°C and a load of 2.18 kg, hereinafter referred to as MFR) is usually 2 to 30 g/10 minutes, especially 3 to 25 g
/ 10 minutes is suitable. MFR is 2g/10
If it is less than 1 minute, the melt viscosity will be high and extrusion moldability will be poor. In addition, if the MFR exceeds 30 f/10 minutes, neck-in of the molten film [in extrusion lamination, the width of the molten film that comes out of the T-die becomes narrower in the space until it comes into contact with the base material; The difference between the width of the molten film at the exit and the width of the laminate film laminated on the base material) is large, making it difficult to produce a coextruded laminate with good quality.

Furthermore, the high load melt flow rate of high density polyethylene (according to JIS K 721G, 190℃, 2
Measured with a load of 1.8 kg, hereinafter referred to as HLMFR)/MF
R is 20 to 40, particularly preferably 25 to 35. High-density polyethylene with an HLMFR/MFR of less than 20 is difficult to manufacture. Also, HLMFR/M
When using high-density polyethylene with an FR of more than 40, it becomes difficult to improve the surface gloss and transparency of the resulting coextruded laminate.

This high-density polyethylene contains commonly used oxygen, heat and UV stabilizers, lubricants, processability improvers and fillers, as well as additives such as clarifying agents, slip agents, anti-blocking agents and anti-static agents. Agents may be added to the extent that they do not essentially change the properties of the coextruded laminate according to the present invention.

(C) Low-density polyethylene The low-density polyethylene used in the present invention is a low-density polyethylene having long chain branches, and has a density of 0.910 to
0.935, /c+a, especially 0.915-0.
930 g/- is suitable. Density is 0.910
Low density polyethylene with less than tr/cIa and density 0
．． Low density polyethylene exceeding 935 g/cIA is difficult to manufacture.

Next, the MFR of low density polyethylene is usually 2~1Og
/10 minutes, and 3 to 9 g/10 minutes is particularly suitable. When the VFR is less than 2 g/10 minutes, the spreadability of the molten film decreases. On the other hand, if the MFR exceeds lOg/10 minutes, the neck-in of the molten film will be large, making it difficult to produce a coextruded laminate with good quality.

Furthermore, the swell ratio of low-density polyethylene (diameter C11 of the tip of the MFR measurement sample 12.5 m11) and MFH
The inside diameter of the measuring orifice (m) and the percentage determined as (N-m)/m are shown.

(hereinafter referred to as SR) is 50% or more, especially 53%
The above are preferred. If SR is less than 50%,
The neck-in of the melt film is large, making it difficult to produce coextruded laminates of good quality.

This low-density polyethylene may be added with oxygen, heat and ultraviolet ray stabilizers, lubricants, processability improvers, fillers, etc., as necessary, within a range that does not essentially change the properties of the coextruded laminate according to the present invention. It may be blended with

(D) Production of coextrusion laminate A membrane coextruder and laminator can be used to melt coextrusion laminate high-density polyethylene and low-density polyethylene on at least one side of the substrate.

A typical method for producing the coextrusion laminate of the present invention is to form a high-density laminate on at least one side of a base material fed at a rate of 50 to 300 m/min using a two-type, two-layer coextrusion laminate forming machine. Examples include a method in which polyethylene and low-density polyethylene are melt-coextruded so that the layer of low-density polyethylene is bonded to the surface of the base material, bonded by pressure between a cooling roll and a pressure roll, and then wound into a roll.

When a two-layer coextrusion laminate molding machine used in the above-mentioned film is used as a manufacturing device for a coextrusion laminate, the method for joining the layer made of high-density polyethylene and the layer made of low-density polyethylene is to Although either an in-die or an outside-die method can be used, the pre-die bonding method is particularly preferred from the viewpoint of manufacturing the coextrusion laminate and the cost of the coextrusion laminating apparatus.

The temperature of the two-layer laminate melt film is 23°C directly under the die.
The temperature is 0 to 330°C, particularly preferably 250 to 320°C. If the temperature of the two-layer laminated molten film is less than 230°C, the spreadability of the molten film will be poor, making it difficult to manufacture the two-layer laminated molten film, as well as causing damage to the base material and the low-density polyethylene layer of the two-layer laminated molten film. Adhesive strength decreases.

Furthermore, if the temperature of the two-layer laminate melt film exceeds 330° C., the neck-in of the molten film becomes large and the stability of the two-layer laminate melt film deteriorates, making it difficult to produce a coextrusion laminate.

In the present invention, the temperatures of the molten films of the high-density polyethylene layer and the low-density polyethylene layer of the two-layer laminate molten film do not need to be the same, and a temperature difference may be actively provided. In other words, in order to increase the adhesive strength between the low-density polyethylene layer and the base material, the low-density polyethylene layer is made higher than the high-density polyethylene layer, or the high-density polyethylene layer is made lower than the low-density polyethylene layer to increase the neck-in of the molten film. You may take other methods as necessary.

Furthermore, in the present invention, ozone gas is sprayed onto the surface of the low-density polyethylene layer of the two-layer molten laminate film between the air gap until the molten two-layer laminate film discharged from the die comes into contact with the base material. A method of increasing the adhesive strength between the base material and the low-density polyethylene layer, the adhesive surface of the base material with the low-density polyethylene layer is subjected to pretreatment such as anchor coating treatment, corona discharge treatment, flame treatment, etc. If necessary, methods such as increasing the adhesive strength may be used.

In the present invention, the two-layer laminated fused film may be bonded not only to one side of the base material but also to both sides.

The low-density polyethylene layer of the two-layer fused laminate film is joined to the base material using a mirror-finished roll as a cooling roll, which cannot normally be used with high-pressure low-density polyethylene because the rolls are difficult to separate. This results in a coextruded laminate with a high-density polyethylene layer having good surface gloss.

The film thickness of the two-layer laminate film in the coextrusion laminate obtained by the method of the present invention is usually 0.005 to 0.05
0 to 0.040 μs is particularly preferable. If the film thickness is less than 0.005 t1n, not only the spreadability of the molten film will become difficult, but also the smoothness and pinhole resistance of the coextruded laminate will deteriorate, which is not preferable. Moreover, if the film thickness exceeds 0.05 (lcae), although it varies depending on the thickness of the base material used, not only the curl of the coextruded laminate becomes large but also the economical efficiency decreases, which is not preferable.

The thickness ratio of the high density polyethylene layer in the two-layer laminate film is 10 to 50%, preferably 10 to 30%. High-density polyethylene layer thickness ratio is 10%
If it is less than that, it becomes difficult to obtain a two-layer laminate film having a high-density polyethylene layer with a uniform thickness. In addition, if the thickness ratio of the high-density polyethylene layer exceeds 50%, the neck-in of the molten film will be large, making it difficult to produce a high-quality coextruded laminate, and also depending on the thickness of the base material used. However, the curl of the coextruded laminate becomes large, which is not preferable.

FIGS. 1 and 2 are enlarged cross-sectional views of a coextrusion laminate obtained by the manufacturing method of the present invention, in which 1 is high-density polyethylene, 2 is low-density polyethylene, and 3 is a base material.

[Function] According to the method for producing a coextrusion laminate of the present invention, coextrusion lamination is performed with a limited layer configuration in which high-density polyethylene is used as the surface layer and low-density polyethylene is used as the support layer that adheres to the base material. It is possible to obtain a coextruded laminate having a two-layer laminate film on at least one side of the base material with processability similar to that of conventional high-pressure low-density polyethylene and surface properties equivalent to those of high-density polyethylene.

[Examples] The present invention will be explained in more detail below with reference to Examples and Comparative Examples.

In addition, surface gloss, blocking resistance, heat resistance, curl resistance, and neck-in in Examples and Comparative Examples were measured and evaluated in the following manner.

(1) Surface gloss Measured according to JIS Z 8741 at an incident angle of 60 degrees. The numerical values indicate that the lamination direction is parallel to the incident and reflected light surfaces. In order to improve the cosmetic appearance of packaging cartons, water-resistant cardboard, etc., it is preferable that the surface gloss is 100% or more.

(2) Blocking resistance JIS Z 15141. : Therefore, 10
The state of blocking between the polyethylene surfaces of the coextruded laminate was observed after adjustment for 5 hours under a load of 14 kg.

O: There is almost no blocking, and there are no scratches on the polyethylene surface.

Δ: Some blocking occurred and some scratches remained on the polyethylene surface.

x: Blocking occurs and significant scratches remain on the polyethylene surface.

In the conditions Δ and It is inappropriate because it damages the value.

It is necessary to be in the 0 state.

(3) Heat resistance According to ASTM D8417-75, DSC-I
I (manufactured by PerkinElmer) under a nitrogen atmosphere for 10
The endothermic peak of a polyethylene laminate membrane punched out to about 10 mg was measured at a heating rate of deg/min. The temperatures shown in the table are the highest peak apex temperature values (hereinafter referred to as melting points) of the endothermic peaks. In order to maintain stable heat resistance in the press varnish coating of packaging cartons and the silicon coating process of release paper, it is preferable that the melting point of the polyethylene in the surface layer is 125° C. or higher.

(4) Curl resistance A circular sample with a diameter of 90+sm was punched out of the coextruded laminate and left at 23°C and 65% RH for 24 hours. ) was measured.

○...The floating height is 30mm or less.

Δ: The floating height exceeds 80 cm and the number of retrievals is less than 1.

X: The number of entanglements is 1 or more times.

The measurement results of △ and Not only does this pose a problem when handling the silicone coating solution, but it can also cause paper jams in the drying and curing cylinder of the silicone coating solution, which can lead to disasters. O's 7fl
It is necessary that the result be a constant result.

(5) Neck-in The neck-in and quality of coextruded laminates were observed.

○: Neck-in is 45 degrees or less, and there is little deviation in thickness near both ends, and the quality is good.

Δ: Neck-in is 55II11 or less, and the thickness is large in the vicinity of both ends, resulting in poor quality.

×: The neck-in exceeds 55 an, the thickness is noticeably uneven near both ends, and the quality is poor.

The observation results of Δ and × show that not only is the product width of the coextruded laminate too narrow, but also that the winding tension is uneven in the width direction, leading to the risk of sagging or breakage of the coextruded laminate. be.

In addition, in order to avoid sagging or breakage, it is possible to trim (cut out) portions where the thickness is uneven, but this is inappropriate because it causes a large amount of loss and is uneconomical.

Preferably, the observation result is 0.

Example 1 One side of corona discharge-treated high-quality paper (basis weight 58 g/rr?) fed at a speed of 90 m/min has a density of 0.
960 g/cat, high density polyethylene with V FR of 20 g/10 min and HLMFR/MFR of 30 and density of 0.917 g/-1 MFR of 7. /10 minutes and low density polyethylene with SR of 58%, diameter 85 mm (L / D -28) and diameter 90 mm, respectively.
(L/D-29) was melted and kneaded in an extruder, and after joining before the T-die, it was introduced into a T-die with a straight manifold, and the lip gap was 0.8 mm, and the width was 750+ul with an inner Deitskel. Through the die slit, the low density polyethylene layer of the two-layer laminated melt film is coextruded so as to be in contact with one side of the above-mentioned high-quality paper, and is pressure-bonded between a mirror roll (cooling roll) and a pressure roll to form high-density polyethylene/low-density polyethylene. A coextrusion laminated paper consisting of polyethylene/woodfree paper was obtained. The temperature of the two-layer laminate melt film is 315°C just below the die lip.
Met.

The evaluation results of the obtained coextrusion laminated paper are shown in Table 1.

Example 2 A coextrusion laminated paper was obtained in the same manner as in Example 1, except that the thickness ratio of high density polyethylene and low density polyethylene in the laminate film was changed as shown in Table 1.

The evaluation results of the obtained coextrusion laminated paper are shown in Table 1.

Example 3 Shiso coextrusion laminated paper was obtained in the same manner as in Example 1, except that the laminate film thickness and the film thickness ratio of high-density polyethylene and low-density polyethylene in the laminate film were changed as shown in Table 1. .

The evaluation results of the obtained coextrusion laminated paper are shown in Table 1.

Comparative Example 1 In Example 1, only low density polyethylene was used in Example 1.
When extrusion lamination was carried out on one side of high-quality paper according to the extrusion conditions described above, continuous processing was difficult due to severe winding around the mirror roll.

The evaluation results of the obtained laminated paper are shown in Table 1.

Comparative Example 2 Except for changing the film thickness ratio of high-density polyethylene and low-density polyethylene in the laminate film as shown in Table 1,
A coextrusion laminated paper was obtained under the same extrusion conditions as in Example 1.

The evaluation results of the obtained coextrusion laminated paper are shown in Table 1.

Comparative Example 3 Instead of the high density polyethylene used in Example 1,
A coextrusion laminated paper was obtained in the same manner as in Example 1, except that polyethylene with a density of 0.944 g/(d, MFR of 2 g/10 min, and HLMFR/MFR of δ was used).

The evaluation results of the obtained coextrusion laminated paper are shown in Table 1.

Comparative Example 4 Instead of the high density polyethylene used in Example 1,
Density is 0.938 g/aR, MFR is IOK
A coextrusion laminated paper was obtained in the same manner as in Example 1, except that high-density polyethylene having an HLMFR/MFR of 38 and HLMFR/MFR of 38 was used.

The evaluation results of the obtained coextrusion laminated paper are shown in Table 1.

Comparative Example 5 Instead of the low density polyethylene used in Example 1,
A coextrusion laminated paper was obtained in the same manner as in Example 1, except that low-density polyethylene having a density of 0.924 g/cffl, an MFR of 7 g/10 min, and an SR of 40% was used.

The evaluation results of the obtained coextrusion laminated paper are shown in Table 1.

Example 4 Using the single-sided coextrusion laminated paper obtained in Example 1, high-density polyethylene and low-density polyethylene were co-extruded on one high-quality paper side in the same manner as in Example 1, and high-density polyethylene/low-density polyethylene was coextruded on one side of the high-quality paper. A double-sided coextrusion laminated paper consisting of density polyethylene/woodfree paper/low density polyethylene/high density polyethylene was obtained.

The obtained double-sided coextrusion laminated paper obtained the same evaluation results as Example 1 except that the curl resistance was further improved.

[Effects of the Invention] According to the method for producing a coextrusion laminate of the present invention, a coextrusion laminate with excellent surface gloss, blocking resistance, heat resistance, and curl resistance, and with small neck-in and good quality can be obtained. It is suitable for use as packaging cartons, silicone-coated release paper, water-resistant corrugated liners, etc.

[Brief explanation of the drawing]

1 and 2 are enlarged cross-sectional views of coextruded laminates obtained according to the present invention. 1...High density polyethylene

Claims (1)

[Claims] At least one side of the base material has a density of 0.940 to 0.97
High-density polyethylene with a density of 0 g/cm^3 and a high road melt flow rate/melt flow rate of 20 to 40 and a low-density polyethylene with a density of 0.910 to 0.935 g/cm^3 and a swell ratio of 50% or more. , the ratio of the thickness of the layer made of high-density polyethylene is 10 to 50% of the total thickness of both resins, and the layer made of low-density polyethylene is melt-coextruded laminated as an adhesive surface to the base material. A method for producing a coextrusion laminate.