JPH09286084A - Polythylenic resin laminate and large-scale clean container formed therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a poleythylenic resin laminate obtaining lamination integrality generating no ply separation even if an adhesive layer is not provided and having high imaact resistance and high cleaning properties and a large-scale clean container composed of said laminate. SOLUTION: This polyethylenic resin laminate consists of at least two layers constituted of a material A composed of a specific high density polyethylene and a material B composed of a polyethylenic resin and the materials A and B characterized by that the difference (▵A-▵B) between the shrinkage factor ▵A (%) calculated from a volume ratio of 200 deg.C/one atmospheric pressure and 50 deg.C/one atmospheric pressure of the material A and the shrinkage factor ▵B calculated from a vol. ratio (%) of 200 deg.C/one atmospheric pressure and 50 deg.C/one atmospheric pressure of the material B is 4.5% or less are laminated in a thickness ratio of 1:4-2:1. Further, the material A of the polyethylenic resin laminate is set to an inner layer and the material B thereof is set to an outer layer to obtain a large-scale clean container.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene-based resin laminate formed by laminating a specific high-density polyethylene and a polyethylene-based resin having a difference in shrinkage ratio of a specified value or less, and a large clean container comprising the same.

[0002]

2. Description of the Related Art Conventionally, a clean container made of synthetic resin having a volume of 20 to 5000 liters, for example, a chemical solution container in the medical field, a food storage container, a physics and chemistry experiment container, a semiconductor cleaning chemical solution container, etc., has a resin component of low elution and high density. It is molded by blow molding or rotational molding using polyethylene.

However, in molding of a single layer of high-density polyethylene, if a material having a small melt index (for example, 0.01 g / 10 minutes) is used in order to make the container larger, the product surface will have various melt fractures. It becomes rough and is not suitable for use in clean containers. Large melt index (eg 3g / 1
If it is used for about 0 minutes or more), the drawdown resistance and impact resistance are low, and the requirements such as drop strength cannot be satisfied. In addition, other resins having impact resistance have a problem of low elution property. For this purpose, a material different from high-density polyethylene, for example, a laminate obtained by combining other polyethylene, polypropylene, polyamide or the like, or a polymer blend is used.

[0004]

Conventional laminates are advantageous over polymer blends because the performance of each resin can be fully exhibited. However, this laminate has a problem that peeling easily occurs between the materials (interlayers), and an adhesive layer or the like is provided between the layers, but in the long term, an intermediate layer (adhesive layer). Therefore, there is a demand for improvement because the adhesive material elutes and peeling occurs due to the alteration of the intermediate layer, and the material (adhesive material), the manufacturing process, the equipment, and the like lead to an increase in cost.

Further, in the blow molding method, a large container of 500 liters or more is difficult to mold, and therefore, it has been molded by the rotational molding method or the like, but there is a problem that delamination occurs between the laminated bodies. It was

Therefore, an object of the present invention is to provide a polyethylene-based resin laminate which has a laminated structure without delamination even if an adhesive layer is not provided, has high impact resistance, and has high cleanliness, and the same. It is to provide a large clean container.

[0007]

Means for Solving the Problems As a result of intensive research to solve the above problems, the present inventors have found that when a specific high-density polyethylene and a polyethylene-based resin are laminated, the shrinkage ratio thereof in the combination is increased. The inventors have found that the problem of the present invention can be solved by stacking layers having a difference of 4.5% or less, and completed the present invention.

That is, in the polyethylene resin laminate of the present invention, the A material has a density of 0.94 to 0.97 g / cm ³ , a melt index of 1 to 9 g / 10 minutes, no additive or an additive amount of 0.1. Low elution high density polyethylene of less than 05% by weight, the material B is a polyethylene resin, and
The following formulas (I), (II) and (III):

[0009]

[Number 4] _{△ A = (V 200A -V 50A} ) / (V 200A) × 100 (I)

[0010]

[Number 5] _{△ B = (V 200B -V 50B} ) / (V 200B) × 100 (II)

[0011]

[Equation 6] △_A -△_B ≦ <4.5 (%) (III) [In the formulas (I), (II) and (III), Δ_A 
Is the shrinkage rate (%) of material A, V_200AIs A at 200 ° C and 1 atmosphere
Specific volume of material (cm^Three / G), V_50A At 50 ° C and 1 atmosphere
Specific volume of material A (cm^Three / G) and also △_B Is B material
Shrinkage (%), V _200BIs the specific volume of material B at 200 ° C and 1 atmosphere
Product (cm^Three / G), V_50B Is the ratio of material B at 50 ° C and 1 atmosphere
Volume (cm^Three / G)], the materials A and B satisfying
Thickness ratio (A material: B material) 1: 4 to 2: 1
Both are polyethylene resin laminates consisting of two layers.

Further, the large-sized clean container of the present invention comprises the polyethylene resin laminate having the material A as the inner layer and the material B as the outer layer.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The high density polyethylene as the material A of the laminate or the inner layer material of the container used in the present invention has a density of 0.94 to 0.97 g / cm ³ . When the density is less than 0.94 g / cm ³ , the crystallinity is insufficient, and the low elution property and rigidity of the molding container are insufficient, while the density is 0.97.
When it exceeds g / cm ³ , the environmental stress cracking property (ESC), which is a characteristic of polyethylene, is inferior, and in the case of use as a cleaning liquid container, the container tends to crack, which is not preferable. In addition, melt index (according to JIS K6760, temperature 19
Measured at 0 ° C and a load of 2.16 kg, hereinafter referred to as MI),
It is from 1 to 9 g / 10 minutes. If the MI is less than 1 g / 10 min, it becomes difficult to mold a large container and the extrusion amount at the time of molding is poor. On the other hand, if it exceeds 9 g / 10 min, the impact resistance is lowered, and the melt viscosity is lowered. It is not preferable because it causes uneven thickness in the container). Further, since the high-density polyethylene has a low elution property, it is necessary to use the above-mentioned high-density polyethylene without addition of various additives or with the additive amount of the neutralizing agent being 0.05% by weight or less.

Next, examples of the polyethylene resin as the material B of the laminate or the outer layer material of the container used in the present invention include low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer and the like. To be

Among the polyethylene resins, low density polyethylene has a density of 0.91 to 0.93 g / cm ³ , MI 2.
It is preferably from 0 to 20 g / 10 minutes. The linear low-density polyethylene has a density of 0.91 to 0.95 g / cm.
³ , MI 2.0 to 20 g / 10 min, and the comonomer is preferably butene-1, hexene-1, 4-methyl-pentene-1 or octene-1, etc., with a content of 1 to 10% by weight. The ethylene-vinyl acetate copolymer has a density of 0.
91 to 0.93 g / cm ³ , MI 2.0 to 20 g / 10
Those having a vinyl acetate content of 1 to 20% by weight are preferable. Such a polyethylene-based resin preferably has the above-mentioned range from the viewpoint of improving moldability and impact resistance, and among these, a linear low-grade polyethylene having excellent mechanical strength and durability improves impact resistance. It is preferable from the top.

Two or more polyethylene resins may be used so that the material B has a multi-layer structure.

Next, in the laminated body or the large-sized clean container comprising the same in the present invention, the above-mentioned specific high-density polyethylene is used as the material A or the inner layer material of the container, and the polyethylene resin is used as the material B or the outer layer material of the container. However, the combination must satisfy the following formulas (I), (II) and (III).

[0018]

[Equation 7] _{△ A = (V 200A -V 50A} ) / (V 200A) × 100 (I)

[0019]

[Equation 8] _{△ B = (V 200B -V 50B} ) / (V 200B) × 100 (II)

[0020]

[Formula 9] Δ _A −Δ _B ≦ 4.5 (%) (III) In the above formulas (I), (II) and (III), Δ _A is the height of the A material of the laminate or the inner layer material of the container. The shrinkage rate (%) of the density polyethylene, V _200A is the specific volume (cm) of the high density polyethylene of the A material or the inner layer material of the container at 200 ° C and 1 atmosphere
³ / g), V _50A is the specific volume (cm) of the material A of the laminated body or the high-density polyethylene of the outer layer material of the container at 50 ° C. and 1 atmospheric pressure.
³ / g), and △ _B is the shrinkage rate (%) of the B material of the laminate or the polyethylene resin of the outer layer material of the container, which is V _200B
Is the specific volume (cm ³ / g) of the B material of the laminate or the polyethylene resin of the outer layer material of the container at 200 ° C. and 1 atmosphere, and V
_50B is the specific volume (cm ³ / g) of the B material of the laminated body or the polyethylene resin of the outer layer material of the container under 50 ° C. and 1 atm.

That is, in the combination of the material A of the laminate or the high density polyethylene of the inner layer material of the container and the polyethylene B of the material B of the laminate or the polyethylene resin of the outer layer material of the container, the shrinkage difference [Δ _A ( _{%) - △ B (%)} , hereinafter the same] shall not exceed 4.5%. Further, in order to further improve delamination and warpage, it is preferable to use a laminate having a combination in which each shrinkage difference is 3.0% or less. The layered product including the combination of the materials A and B having a difference in shrinkage ratio of more than 4.5% causes delamination or warpage. In addition, the impact resistance of the container is reduced and deformation occurs. Even when the polyethylene resin as the material B of the laminate has a multi-layer structure, it is necessary to use a combination of layers having the same shrinkage ratio difference.

The high density polyethylene of material A and B
The specific volume of the polyethylene resin of the material at each temperature is
It can be determined by measuring PVT characteristics.

Here, the PVT characteristic means the pressure (P) -in a wide temperature range from the solid phase of the thermoplastic material to the molten phase.
It refers to the interrelationship of volume (V) -temperature (T), and the equation of state is used for its quantification. In the present invention, PV
It was measured by a T tester. Next, the polyethylene resin laminate of the present invention is obtained by laminating the high density polyethylene of material A and at least one polyethylene resin of material B under the combination of the above conditions. The laminating method is to guide the A material and the B material to a set of common dies by using two or more extruders and bring the A material and the B material into contact with each other in the inside or the die opening to form a single laminated body. Co-extrusion molding, blow molding in which a gas is blown after forming this co-extrusion into a cylindrical parison, press molding in which a sheet of material A and material B that has been previously molded into a sheet shape is preheated and then heated or pressed, or a sheet shape in advance Placing the corresponding pellets, powders or crushed products on the A material or B material molded in 1., press-molding by heating them after preheating, and further laminating the powders of A material and B material in sequence by rotational molding. Of these, it can be preferably used for rotational molding. The temperature during each of the above molding is
It is preferably carried out at 150 to 300 ° C.

Further, the thickness ratios of the A material and the B material of the laminated body are as follows, in order to improve the low elution property (reduce the elution particles) and the impact resistance. A
Material: B material = 1: 4 to 2: 1. The thickness of the laminate can be appropriately selected depending on the application, but is generally 0.5 to
It is 30 mm, and preferably 1.0 to 30 mm.

The large clean container of the present invention can be manufactured by a blow molding method, a rotational molding method, or the like. For example, in the above-described blow molding method of two kinds and two layers of the material A for the inner layer and the material B for the outer layer, each material is supplied to two extruders and the temperature is 150 to 30.
It is melted at 0 ° C. and extruded into a cylindrical parison so that the material A is the inner layer and the material B is the outer layer, and the extruded parison is sandwiched between molds and blown with a pressurized gas from a blow pin to cool and mold. When the outer layer B material has two layers, one more extruder may be added and melt extruded in the same manner to extrude into a parison of three types and three layers, and the parison is molded in the same manner.

Further, in the case of molding the two kinds of two layers of the material A for the inner layer and the material B for the outer layer by the rotational molding method, for example, the material B for the outer layer is put into the mold and the inner wall of the mold is rotated by the centrifugal force. Apply evenly and rotate the mold at 1-30 rpm 1
After heating and melting the resin at a temperature of 50 to 350 ° C., water is sprayed on the outer surface of the mold and cooled to 100 ° C. or lower, and then the A material for the inner layer is put into the mold. This may be heated and cooled as in the case of the outer layer B material to form the inner layer.

The large-sized clean container of the present invention can be molded into a large capacity because it is made of the above-mentioned specific laminated body. Particularly, for the super-large container having a volume of 500 to 5000 liters, the method of the present invention. Therefore, it is preferable to obtain a laminated body by rotational molding. The thickness ratio of each layer in the laminated body of the material A for the inner layer and the material B for the outer layer of the container is low elution property (reduces elution particles in the storage liquid) and impact resistance (falling strength etc.) of the vessel. From the viewpoint of improvement, the inner layer: outer layer = 1: 4 to 2: 1. The average wall thickness of the container can be appropriately selected depending on the volume, but is generally 0.5 to 30 mm.
In particular, 5 to 30 mm is preferable for a container of 500 liters or more.

[0028]

Embodiments of the present invention will be described below in detail. The high density polyethylene (HDPE) of material A of the laminate and the linear low density polyethylene (L-LDPE) of material B of the laminate, which are the raw materials, were those shown in Table 1.

[0029]

[Table 1] (Note) The specific volume A is the specific volume of 1 atm and 200 ° C, and the specific volume B is the volume ratio of 1 atm and 50 ° C. The specific volume was measured under the PVT tester and measurement conditions shown in Table 2. The shrinkage ratio Δ (%) = [specific volume A (cm ³ / g) -specific volume B (cm ³ / g)] / [specific volume A (cm ³ / g)] × 100.

[0030]

[Table 2]

Examples 1 to 4, Comparative Examples 1 and 2 Sample Preparation Method-1 [For Deformation (Warp) Evaluation] A material for laminate (HDPE) and B for laminate shown in Table 1
For each material (L-LDPE), injection molding machine (mold clamping force 150 ton, injection capacity 8 oz, resin temperature 250
℃, mold temperature 80 ℃) width 100mm, length 350
mm, thickness 3mm sheet is formed, length 20 from this
Take out the 0 mm test piece, press machine (30 ton),
After heating both the upper and lower sides of the press plate to 250 ° C., the test pieces of material A and material B were preheated on the press plate for 5 minutes, and then 1
A test piece for deformation (warpage) evaluation was obtained by applying a pressure of 3 kgf / cm ² for one minute to integrate them and cooling at room temperature.

Sample Preparation Method-2 [Test Piece for Delamination] About material B, width 100 mm, length by injection molding machine (mold clamping force 150 ton, injection capacity 8 ounce, resin temperature 250 ° C., mold temperature 80 ° C.) A sheet having a length of 350 mm and a thickness of 3 mm is formed, and a test piece having a length of 200 mm is taken out from the sheet.
After the temperature is lowered to 30 ° C. and the lower side is set to 30 ° C., the injection-molded sheet of the material B is placed on the lower side of the press plate, the pellets of the material A are evenly placed thereon, and the upper press plate is brought close to it and preheated for 5 minutes. A test piece for delamination was obtained by applying a pressure of 3 kgf / cm ² for one minute to integrate them and cooling at room temperature.

The physical properties of these test pieces were evaluated according to the following criteria, and the results are shown in Table 3.

[0034]

[Table 3]

Examples 5 to 8 and Comparative Examples 3 to 7 Sample preparation method-3 [for cracking test by elevating ball test at -18 ° C. and elution particle test] A material for laminate (HDPE) and laminate shown in Table 1 B material (L-LDPE) for use in a combination as shown in Table 4 and by the following method by the rotational molding method, the cross-sectional dimension of the container 300 mm × 200 m
A two-kind two-layer hollow container and a test piece having a square cross-section of m, a wall thickness of 10 mm, and a volume of 20 liters were molded.

First, the outer layer material (material B) is put into the mold,
After molding the outer layer at a mold heating temperature of 300 ° C., the mold was cooled with cooling water at 20 ° C. until the mold reached 100 ° C. The inner layer material (A material) was added to this, the mold heating temperature was set to 300 ° C., the inner layer was molded, the mold was cooled again to 20 ° C. until the mold reached 100 ° C., and then the molded product was taken out and cooled at room temperature. .
At this time, the ratio of the inner layer (A material) / outer layer (B material) is set to the ratio shown in Table 4, and the outer layer material (B
A hollow container was prepared by adjusting the input amounts of the resin for the material) and the resin for the inner layer material (the material A). 160m width from the obtained hollow container
A sheet-like test piece of m × length 240 mm, wall thickness 10 mm was cut out, and a weight was put on it to prevent the cut sheet from warping.
A test piece having no sled was prepared by allowing it to stand for 2 hours.

The physical properties of these test pieces and containers were evaluated according to the following criteria, and the results are shown in Table 4.

[0038]

[Table 4]

(Note) (1) Deformation (warpage): The long side ends of the laminated test pieces obtained by injection-molding and press-molding each material A and material B were fixed on the surface plate immediately after molding, and 23 After standing still in a thermostatic chamber at a temperature of 72 ° C. for 72 hours, the degree of warpage of one end of the remaining long side was measured. The criterion for evaluation is that the amount of warp is “large” when 5 mm or more, and less than 5 mm 1
mm or more was "medium", and less than 1 mm was "small". (2) Delamination: A test piece obtained by injection-molding and press-molding each material A and material B was allowed to stand for 72 hours at 23 ° C. in a constant temperature room for 24 hours after molding, and then cut in a direction orthogonal to the joint surface. Then
The cross section was magnified 100 times using a microscope and observed for the occurrence of peeling of the joint. (3) Cracking test by -18 ° C falling ball test: width 160 mm x length 240 mm cut out from hollow container, wall thickness 10 m
After the sheet-shaped test piece of m was left at -18 ° C for 24 hours, a steel ball with a mass of 1 kg was placed at a height of 100 cm in the same atmosphere.
Was dropped to the center of the test piece, and the presence or absence of cracks was visually observed. The same test was carried out 10 times, and when a crack occurred, it was determined to have a crack. (4) Elution particle test: good cross-section of container made by rotational molding method 300 mm x 200 mm, wall thickness 10 m
10 liters of ultrapure water was placed in a 2-kind 2-layer hollow container having a square cross section with a volume of 20 liters and shaken for 10 seconds to wash the inner wall of the container and discard the water. Next, 10 liters of ultrapure water was placed in this container, and washing water after shaking for 30 seconds was subjected to 10 times measurement of the number of particles of φ0.2 μm or more present in 1 ml by a particle counter made by Rion, and the average value was calculated.

As can be seen from Comparative Examples 1 and 2, if the difference in heat shrinkage ratio is out of the range of the present invention at the same wall thickness ratio, delamination occurs during cooling after molding and deformation (warpage) also increases, which is not preferable. . The wall thickness ratio is outside the range of the present invention (Comparative Example 3 to
In 7), the number of eluted particles is high and the cleanliness is insufficient (Comparative Examples 3 to 5), or cracking occurs in the -18 ° C falling ball test (Comparative Examples 6 to 7), which is not preferable because the impact resistance is insufficient. On the other hand, in Examples 1 to 8 of the present invention,
It does not cause delamination during cooling after molding, has little deformation (warpage), is excellent in impact resistance, has few elution particles, and has high cleanliness. Further, the container is also good in impact resistance and has few eluted particles.

[0041]

INDUSTRIAL APPLICABILITY As described above, the laminate of the present invention has no delamination without providing an adhesive layer, is excellent in deformation resistance and impact resistance, and has low elution property, and can be used in various applications. However, it is particularly useful for containers. Further, since the container can have both impact resistance and low elution property, it is possible to provide a large container having particularly high cleanliness. Furthermore, since no adhesive layer is used, 3
There is no need for material, manufacturing process, and equipment costs due to the number of layers or more.

Claims (3)

[Claims] 1. The material A has a density of 0.94 to 0.97 g / cm.
³ , melt index 1-9 g / 10 min, low elution high density polyethylene with no additive or additive amount of 0.05 wt% or less, B material is polyethylene resin,
And the following formulas (I), (II) and (III): [Formula 1] Δ _A = (V _200A −V _50A ) / (V _200A ) × 100 (I) [Formula 2] Δ _B = (V _{200B -V 50B) / (V 200B} ) × 100 (II) [expression 3] _{△ a - △ B ≦ 4.5 (} %) (III) [ the above formula (I), in (II) and (III) , △ _A
Is the contraction rate (%) of material A, V _200A is A at 200 ° C and 1 atmosphere
The specific volume of the material (cm ³ / g), V _50A is the specific volume of the material A (cm ³ / g) at 50 ° C. and 1 atmosphere, _ΔB is the shrinkage rate of the material _B (%), and V _200B is The specific volume of material B (cm ³ / g) at 200 ° C. and 1 atmosphere, V _50B is the specific volume of material B (cm ³ / g) at 50 ° C. and 1 atmosphere] A polyethylene resin laminate comprising at least two layers laminated at a ratio (A material: B material) of 1: 4 to 2: 1. 2. The polyethylene resin laminate according to claim 1, wherein the polyethylene resin is linear low-density polyethylene. 3. A large clean container in which the material A of the polyethylene resin laminate according to claim 1 or 2 is an inner layer and the material B is an outer layer.