JPH06545B2 - Flexible dispensing tube - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to flexible dispensing tubes, particularly flexible tubes made of multilayer flexible sheet material, commonly used for packaging paste-type products.

(Prior Art) Single layer, thick metal foils have long been used for packaging and dispensing paste type products. However, a distinct drawback with metal tubes is that they are much more expensive than other tube constructions, yet they are prone to indentation and tend to crack even with moderate bending.

Relatively recently, a large share of the tube market share has been dominated by flexible sheet materials with multilayer polymers. A typical tube has an inner heat sealable layer, an outer heat sealable layer, and a barrier layer therebetween. Additional layers may be used in conventional sheet materials to impart other properties or qualities.

These sheet materials can also be sandwiched with non-polymeric layers such as paper or thin metal foils to provide special performance.

For example, as is well known, a layer of thin aluminum foil can be used as a high quality barrier layer. If a foil is used, it is common to use a polymer with strong adhesion to adhere it to the adjacent layers.

Again, as is well known, layers of paper may be used. This can provide dimensional stability and a white background with an aesthetically pleasing, sterile and clean-feeling appearance.

PROBLEMS TO BE SOLVED BY THE INVENTION While known sheet materials have been successful in the commercial market, existing tube constructions have certain problems. For example, some products are too stiff to use the polymeric tube structure for packaging.

A major problem with tube breakage is the chemical activity of the packaged product on tubes with aluminum foil. Due to the chemical attack of the product, small cracks called stress cracks occur in the polymer between the foil and the product. The product then penetrates the polymer from the stress cracks and attacks the foil, thus weakening the adhesion between the foil and the adjacent layers. Alternatively, the product attacks the interfacial bonds between the polymer layers, weakening the adhesion between these polymer layers. In both cases, due to the breaking of the bond,
This results in early rupture of the tube.

To solve the problem of stress cracking, it is known to use a thick layer of ethylene acrylic acid (EAA) as the product contact surface. Although EAA has a fairly high resistance to stress cracking, it is relatively expensive and it is highly desirable to look for a cheaper alternative material. Also, during tube processing, the processing equipment scrapes small particles of EAA from the surface.

These particles, called Polydust, can adhere to the tube and even become trapped within the tube. The material used in contact with the hygiene product is preferably one that is acceptable for contact with the product, and it is highly desirable to have no type of contaminant inclusions in the product.

Therefore, it is desirable to find a material that has high stress crack resistance and does not generate polydust in the processing equipment.

Numerous attempts have been made in the packaging industry to solve this problem in tube construction, and in particular certain polymers such as polyethylene have been provided to the packaging industry as improving stress crack resistance, but nonetheless. The problem of stress crack resistance remains unsolved. Therefore, it remains for the inventor to solve this problem by making the tube from an improved sheet construction material and performing extensive testing on many alternative constructions.

The inventor has solved this problem of stress cracking by making the tube from an improved sheet structure.
The prior art was not aware of making tubes from sheets with an LLDPE (Linear Low Density Polyethylene) outer layer.

After many experiments, the inventor found that LLDPE was used as the outer layer.
Therefore, it was surprising that the stress crack resistance was obtained as compared with those having other outer layer materials.

Japanese Utility Model Laid-Open No. 56-32054 discloses a soft drink pouch made of a sheet having a laminated structure of low or medium density polyethylene (LDPE or MDPE) film, aluminum foil and drawn high density polyethylene (HDPE). To do. Although this sheet has a satisfactory strength as a soft drink pouch, it cannot solve the problem of environmental stress cracking in a tube for dispensing a paste-like material. Structures with HDPE as the outer layer cannot overcome the problem of stress cracking.

Further, Japanese Patent Laid-Open No. 53-113684 discloses a method for producing a container body having an outer layer of polyethylene resin. Although tubes already made from sheets with high or low density polyethylene in the outer layer already exist, such structures are also known to be susceptible to environmental stress cracking. this is,
This is nothing but the problem to be solved by the present invention.

Furthermore, Japanese Unexamined Patent Publication No. 52-94288 discloses an extruded tube and a method for producing the same. The tube is made from a sheet structure with paper and aluminum foil bonded with electrodeposited fused synthetic resin. This is similar to the structure known as a laminated structure having an outer layer of synthetic resin and is weak against stress cracks.

After all, these three prior art references do not suggest the use of LLDPE outer layers to solve the problem of stress cracking.

(Means for Solving the Problems) A plurality of layers are LLDPE layers so as to form an integral structure,
A multilayer sheet material in which a first adhesive layer, a barrier layer, a second adhesive layer, a first polyethylene layer, a paper layer, a second polyethylene layer and a heat-sealable polymer layer are firmly adhered to each other in this order. By a tube made of
It turns out that a great improvement can be achieved.

The thickness of the first polyethylene layer is about 18 to 76μ (about 0.7 to 3.0 mils). The heat-sealable layer is L
It is LDPE. As used herein, LLDPE shall collectively refer to both homopolymers and copolymers of linear low density polyethylene. Preferably LLDP
The thickness of the E layer is 18 to 76μ (0.7 to 3.0 mils),
The barrier thickness is 8.9 to 51μ (0.35 to 2.0 mils) and the thickness of the first polyethylene layer is 18 to 76μ (0.
7 to 3.0 mils) and the sum of the thickness of the second polyethylene layer and the thickness of the outer layer is about 51 to 127 μ (about 2.0 to 5.0 μm).
Mil).

In the most preferred sheet material, the thickness of the LLDPE layer is about
30.5μ (about 1.2 mils) and foil thickness is 8.9μ (0.35 mils). Also, in this preferred sheet material,
The sum of the thickness of the LLDPE layer and the thickness of the first adhesive layer is 51 to 127μ (2.0 to 5.0 mils).

In another preferred construction, the heat sealable polymer is polyethylene.

In yet another preferred construction, an additional polymer layer is included between the heat sealable polymer layer and the second polyethylene layer.

The first and second adhesive layers are effective in adhering the foil to the first polyethylene layer and the LLDPE layer, and the thickness of each layer is similar to the sheet material described above. In some embodiments, the second adhesive layer and the first polyethylene layer can include up to 100% ethylene methyl acrylate (EMA) copolymer as a blend component.

(Operation) In FIG. 1, numeral 10 indicates the entire cross section of the multilayer sheet material. Layers 12, 14, 18 are low density polyethylene (LDPE). Layer 16 is paper. Layer 32 is LLDPE (linear low density polyethylene).

Layers 26 and 30 are EAA. Layer 28 is aluminum foil.

Considering the surface of the multilayer sheet material 10, the first layer 12
Is LDPE, the second layer 14 is LDPE blended with a color pigment, the third layer 16 is paper, and the fourth layer 18 is
Is LDPE. The EAA copolymer adhesive layer 26 adheres layer 18 to the next metal foil 28, preferably an aluminum foil.
Layer 30 is EAA and effectively adheres LLDPE layer 32 to foil 28.

Layers 12 and 14 together act as a heat seal layer, forming a bond on the tube sidewall. At this joint, the layers
A portion of the surface of 12 is sealed against a portion of the surface of layer 32 to form a lap seal. Similarly, layer 30 is effectively used as part of the heat seal on the heat seal side of the sheet material, with layers 30 and 32 working together as needed to form the heat seal. Layer 30 also acts as a barrier between foil 28 and product 37, preventing chemical attack on the foil by the product. The paper layer 16 is used for its well known function of providing dimensional stability to the sheet material. Aluminum foil 28 is used as a barrier to prevent the transmission of gas and light passing through layers 14 and 16. Also, this aluminum foil 28 is a layer of paper 16
At the same time, it also serves to impart dimensional stability to the sheet material.

In another embodiment of the invention shown in FIG. 2, the adhesive layer 11
8 and 126 are ethylene methyl acrylate copolymer (E
1) by blending (MA) at 0-100%.
It is a modified version of 8 and 26. (A 100% blend is pure EMA, but this is included here for formulation purposes.) This EMA blend effectively adheres two adjacent layers.

A tube according to the present invention can be easily made from sheet material as in Figures 1 and 2 using conventional methods on conventional equipment,
The tube can be processed, filled and sealed. As you can see from the test data below,
The tubing made from the structure shown has a thickness of 253μ (10 mils), which has significantly better impact resistance than the 330μ (13.0 mil) prior art structure shown in FIG. There is. The latter is further shown in Table 1 as prior art structure A. In the present invention, the foil thickness is 8.9μ (0.3
5 mils) and the thickness of LDPE layer is 8.9μ
(0.35 mils) and the EAA layer thickness is 58μ (2.3
Mil) is decreasing. Therefore, the material savings as a whole are considerable.

In the greatest improvement provided by the present invention, layer 32 of FIG. 1 and corresponding layer 132 of FIG. 2 are made of LLDPE. This improvement relates to the protection of foil 28 and to the adhesion of foil 28 at the interface with layer 30.
It is also associated with enhanced interfacial adhesion between layers 30 and 32.

As in the prior art in FIG. 3, typically 51 μ (2.0 mils) EAA and 30.5 μ (1.2 mils) LDPE are used. Such structures are vulnerable to certain chemical products that should be contained in the tube, and the failure known as stress cracking renders the product unpackable. In this case, the physical stress and the presence of certain chemical products cause minute cracks in the LDPE layer. This crack may effectively allow the chemical product to penetrate the LDPE layer, which may effectively weaken the adhesion between layers 330 and 332 . The chemical may also penetrate the EAA layer. The penetration of the product through the EAA layer promotes an attack on the interlaminar adhesion between the EAA layer and the foil. A typical result is weak adhesion at the interface between the foil and the EAA layer and in some cases results in visible corrosion of the foil. Once the bond is weakened, the integrity of the multi-layer structure is destroyed and the structure is unable to perform its function properly.

In an attempt to improve stress crack resistance, the prior art uses EAA instead of LDPE as layer 332 . This replacement is partially successful, but expensive EA
Since A is used, the cost is considerably high. Functionally, however, the EAA surface is susceptible to scratching and requires very careful handling, which is undesirable in an industrial manufacturing operation. Surprisingly, replacing the LDPE with an inexpensive LLDPE significantly improves the stress crack resistance, at least comparable to EAA.

As will be readily appreciated, the outer layers of the tube, such as layers 12 and 14 of FIG. 1, can be selected from similar materials as layers 30 and 32. Examples of acceptable materials are LDPE, LL
DPE, EAA, EMA, medium density polyethylene (MDP
E), high density polyethylene (HDPE), and ethylene vinyl acetate (EYA).

Example 1 In the manufacture of tubes from the multilayer sheet structure of the present invention, 51μ (2 mils) of colored LDPE was 41μ (1.6 mils).
Paper was extrusion coated. 18μ on the uncoated surface of the paper
(0.7 mils) LDPE laminant was extrusion coated and 29μ (1.15 mils) LDPE was extrusion coated over the coated side. This LDPE laminar layer is 8.9μ
The first surface of a (0.35 mil) aluminum foil was extrusion laminated using 25 μ (1.0 mil) EAA as the laminant. Finally, the second surface of the foil was coextruded coated with 51μ (2.0 mils) EAA and 30.5μ (1.2 mils) LLDPE. This EAA is adjacent to the foil. The multilayer tube wall thus produced has a thickness of 250 μ (10.0 mils) and is as shown in FIG.

Example 2 A tube was made from the same sheet as Example 1 except that the extruded laminant contained EMA, as in layers 118 and 126 of FIG. Layer 118 is 100% EMA
And layer 126 is a blend of 75% EMA and 25% EAA. This 30.5 μ (1.2 mil) surface is the LLDPE structure shown in FIG.

Example 3 51 μ (2 mil) pigmented L on 41 μ (1.6 mil) paper 116
DPE 114 was extrusion coated (Figure 2). The uncoated surface of the paper was extrusion coated with 18μ (0.7 mil) LDPE 118 . The pigmented LDPE coated surface of the paper was then further coated with 38μ (1.5 mils) LDPE 112 by extrusion coating. 18μ (0.7 mil) aluminum foil 128 , 84μ (3.
(3 mil) EAA 124 , 18μ (0.7 mil) LD
Extrusion coated on PE. Finally, E of 51μ (2.0 mils)
AA 130 and 30μ (1.2 mils) LLDPE 132 were coextrusion coated onto the exposed foil surface. In this case, EA
A 130 is adjacent to the foil. A tube as shown in FIG. 4 was manufactured from the sheet material having a thickness of 330 μ (13.0 mils) manufactured in this way.

Examples 4 to 9 Tubes manufactured in other ways are also shown in Table 1 together with Examples 1 to 3.

The sheet material of the above example was processed into a dispensing tube by a known method. That is, by forming a lap seam in the longitudinal direction by heat sealing techniques to make a tube having a diameter of 3.4cm (1 _^11/32 inch). The tube was then cut to length and a conventional insert was used to injection mold the head at one end and cap it. The tube was filled with the product and then sealed at both ends. The filled tube was then tested for strength testing. This test was performed immediately after manufacture and after aging for a predetermined period.

Stress Crack Test In evaluating the stress crack resistance, the structure of the example was compared with a structure according to prior art A and another structure according to prior art B and C.

In one stress crack test, 4 tubes made of the sheet material of Example 2 and 4 tubes made of the sheet material according to Prior Art A were filled with mineral spirits. Two tubes each at 49 ° C (120 ° F) and 6
Stored at 0 ° C (140 ° F). After 5 days both sets of Prior Art A tubing experienced stress crack fracture, but the tubing of Example 2 did not rupture even after 1 month. In another stress crack test for the structure of Example 2 and prior art A, the tube was filled with toothpaste and then 49 ° C (120 ° C).
Stored in F). One month later, squeezing was performed to compare the integrity of the seals and the tube according to Prior Art A broke at a lower squeezing pressure than the tube of Example 2.

In yet another stress crack test, prior art A,
B and C and Example 2 were compared. The tubes were filled with mineral spirits and then stored horizontally. Two sets of tubes made from each laminated sheet are used at 49 ° C (120 °
F) and stored at 60 ° C (140 ° F). In the case of the prior arts A and C, stress cracking occurred within 1 week. In the case of Prior Art B or Example 2, it did not occur. A squeezing test was performed on the remaining tubes. Example 2 and Prior Art C were determined to be the same. Prior art B was better than this, and prior art A was the worst.

In the processing test, a pressure higher than the usual reduction pressure in an industrial side seaming device was applied to the tubes of Prior Art B and Example 2 to see the susceptibility to polydust formation. During testing of the tube of Prior Art B, polymer fines were accumulated, indicating a polydust problem. No polydust was observed in the tube according to Example 2 during a similar comparative test.

From the above tests of the tube of Example 2 against the prior art tube, the use of LLDPE as the sealant layer improves the stress crack resistance over the use of LDPE (Prior Art A) and the stress crack resistance of LLDPE is EAA. (Prior art B and C), and further LL
It is concluded that DPE is less likely to produce polydust in processing equipment than EAA (processing test of prior art B tube).

As explained above, the present invention relates to a tube made of a multi-layer sheet material, which has better stress crack resistance than some prior art and is comparable to some prior art. It is found to have stress crack resistance and better resistance to polydust formation.

EFFECTS OF THE INVENTION The present invention solves the problem of stress cracking found in numerous tubes known to date. The prior art also partially solved this problem by using a thick layer of ethylene acrylic acid (EAA) on the side facing the content product.

But it was far from a complete solution. This is because EAA is too expensive and economically inferior.

Therefore, the present inventor has conducted repeated research for a material that is inexpensive and has satisfactory stress crack resistance, and as a result,
The intended purpose was achieved by forming the LLDPE layer on the side facing the tube content product. This is also clear from the stress crack test described above. The present invention has excellent stress crack resistance as compared with the conventional tube having the LDPE layer, and also makes it possible to obtain a satisfactory tube at a much lower cost as compared with the conventional tube having the EAA layer.

[Brief description of drawings]

FIG. 1 is a cross section of one embodiment of a multilayer sheet material used in the present invention, FIG. 2 is a cross section of another embodiment of the same multilayer sheet material, and FIG. 3 is a prior art sheet material. FIG. 4 is a partial sectional view of a flexible dispensing tube for product packaging made of the sheet material of the present invention. In the figure, 10 is a multilayer sheet material, 12, 14, 112, 114 are heat-sealable layers (LDPE, LLDPE, etc.), 16, 116
Is a paper layer, 18, 118 is an adhesive layer (LDPE, LLDPE, etc.), 32, 132 is LLDPE, 26, 126, 30 , 130 are an adhesive layer (EAA, etc.), 28, 128 are barrier layers (metal foil, especially aluminum foil) Layer), 34 is a flexible dispensing tube.

Claims (6)

[Claims] 1. A flexible dispensing tube comprising a multi-layer sheet material in which the following layers are intimately adhered to each other in the following order to form a unitary structure. (A) LLDPE (linear low-density polyethylene) layer, (b) first adhesive layer, (c) barrier, (d) second adhesive layer, (e) first polyethylene layer, (f) paper A layer, (g) a second polyethylene layer, and (h) a heat-sealable polymer layer. 2. The tube according to claim 1, wherein the barrier layer is a metal foil. 3. The tube according to claim 1, wherein the heat-sealable polymer layer is polyethylene. 4. The tube of claim 1 including an additional polymer layer between the heat sealable polymer layer and the second polyethylene layer. 5. The tube according to claim 1, wherein the LLDPE layer thickness is 18 to 76 μ (0.7 to 3.0 mil) and the barrier layer thickness is 8.9 to 51 μ (0.35 to 2.0 mil). 6. The two adhesive layers comprise 10 as a blend component.
A tube according to claim (1) comprising up to 0% ethylene methyl acrylate copolymer.