KR20050107637A - Multilayer laminate with excellent heat resistance and gas barrier properties - Google Patents

Abstract

Each of the inner and outer layers comprises 80 to 99% by weight of an amorphous polyester resin having a crystallinity of less than 20% and 20 to 1% by weight of a polyamide-based oxygen barrier resin. The oxygen scavenger of the transition metal derivative is 0.001 to 5 wt%, wherein the intermediate layer has a polycarbonate resin as a main component, and is located between the outer layer and the inner layer, and the relative weight of the layer satisfies the following formula.

Where a is the weight per unit area of the outer layer, b is the weight per unit area of the intermediate layer, and c is the weight per unit area of the inner layer.

Description

Multilayer laminate with excellent heat resistance and gas barrier properties

The present invention relates to multilayer laminates that can be processed in the form of multilayer sheets, films, food or beverage containers, or other multilayer structures. More specifically, the present invention relates to a multilayer packaging for food packaging having excellent heat resistance while using amorphous polyester.

The packaging industry, including metal or glass containers, has been around for centuries. Since the sixties, polymeric high barrier materials such as PVDC have been used, and EVOH was first commercialized in the early seventies. However, the improvement of coextrusion technology, which allows for a single pass of an effective combination of multilayer structures, is only a few decades ago, and the barrier plastics industry has developed significantly.

The use of plastic based barriers and selective barrier structures has increased and recently applied to food, pharmaceutical, medical, chemical and industrial packaging.

Containers made of plastic are the choice of consumers and packers for their light weight, durability and non-breaking reasons. Plastic containers can be made of various polymers. Depending on the polymer selected, the properties of the vessel, such as gas or water vapor barrier properties, impact resistance, transparency and heat resistance, can be obtained.

Billions of containers and packaging products are made each year to pack food and beverage products or other household items. In order to make such containers, various materials are used depending on the particular use or application. Container manufacturers and food. Beverage manufacturers need to balance the design requirements for packaging applications against the economics of producing certain containers. Design considerations include visually acceptable container characteristics such as surface gloss and reflectivity, cleanness of the container wall, transparency and blurring of the container wall material. These visual characteristics are important for selecting cost effective packaging materials for both functional and aesthetic reasons.

Polyolefins such as polyethylene and polypropylene have barrier properties to water vapor, but are generally unsatisfactory in terms of transparency and gloss. Although exhibiting gas barrier properties and satisfactory in terms of transparency, polyvinyl chloride is poor in heat resistance.

The application of various amorphous polyamide compositions and their various uses is well known. Such compositions are generally characterized by high transparency and lack of precise melting points. Applications of such compositions include films, sheets, laminates and other shaped articles. Some of these compositions, however, have relatively poor thermal properties and therefore exhibit limited use in relatively low temperature applications.

Examples of such compositions are shown in US Pat. Nos. 2,715,620 and 2,742,496 as polyamides of isophthalic acid and hexamethylenediamine. As shown in US Pat. No. 4,250,297, such compositions have low dimensional stability at high temperatures, using such isomeric mixtures of 2,2,4- and 2,4,4-trimethylenehexamethylenediamine instead of hexamethylene diamine. It was suggested to overcome the shortcomings.

Amorphous polyamides based on terephthalic acid and isophthalic acid or derivatives thereof and hexamethylenediamine are also disclosed in US Pat. Nos. 3,379,696 and 3,475,387. Such compositions exhibit improved thermal properties compared to isophthalic acid and hexamethylenediamine, but have problems with the transparency of products made from such compositions, and when the molar ratio of isophthalic acid to terephthalic acid is used too low, In use, there is a problem that crystallization of the polymer occurs.

US Pat. No. 2,766,222 discloses transparent compositions made from isophthalic or isophthalic acid / terephthalic acid mixtures and metaxylenediamines, which compositions are molded articles of high transparency, good thermal and chemical resistance, excellent tensile and impact strength It is also disclosed to be suitable for making. Softening points of 150-170 ° C. for such compositions are disclosed by way of example. In addition, the transparency of the composition discloses that at least about 40 mole percent of isophthalic acid will be replaced by terephthalic acid.

The usefulness of metaxylenediamine group containing polyamides in molding containers is revealed in US Pat. No. 4,398,642, wherein the multilayer container is an inner layer of polyester resin, an intermediate layer composed of metaxylene group containing polyamide resin, and moisture An outer layer made of synthetic resin having an impermeability. The metaxylene group-containing polyamide interlayers are known to provide gas barrier properties. However, the glass transition temperature of the metaxylene polyamide is about 80 ° C., so that the container is susceptible to high temperature exposure, such as warping during the filling of the container hot.

U. S. Patent No. 4,535, 901 discloses a multilayer container consisting of an odd number of layers having an innermost layer of polyester resin and an outermost layer and at least one intermediate layer consisting of metaxylene group containing polyamides. have. The intermediate layer should be completely covered by both the inner and outer layers which provide good water resistance, high chemical resistance and high hygienic quality. Upon absorption of water, it is known that the non-oriented metaxylene polyamide resins lower the glass transition temperature and the crystallization temperature. According to a product report titled "Toyobo nylon MXD6" published by Toyota Corporation, "unoriented MXD6 turns white when it absorbs water from air." Water absorption lowers the glass transition temperature and the crystallized temperature so that it may crystallize the MXD6 even at room temperature. Non-oriented MXD6 products are not suitable where long transparency is required. Therefore, this patent is a multilayer product of PET / MXD6 / PET structure, and the PET outer layer completely surrounds the MXD6 layer to prevent the MXD6 layer from absorbing water.

Similarly, EP 0 186 154 discloses a nine-layer parison, a method for making it and a multilayer container made from the parison. Here, the nine-layer structure has two outer layers and one central layer of PET and two intermediate layers of MXDA nylon, and are positioned between the PET layer and the MXDA nylon layer to bond the PET layer and the MXDA nylon layer. It consists of four floors.

Laminates using PC instead of PET in a multilayer structure similar to the above have been disclosed in several patents. For example, US Pat. No. 4,513,037 discloses a multilayer hollow comprising at least one inner PC layer, at least one outer PC layer and at least one intermediate layer of thermoplastic resin exhibiting gas barrier properties between the inner and outer PC layers. The PC container is disclosed. Various resins are mentioned as suitable for coextrusion blow molding, and examples thereof include polyester, nylon, polyvinylchloride, polyvinyldiene chloride, polyvinyl alcohol, acrylonitrile and copolymers of ethylene and vinyl alcohol. Lose. Such multilayer PC containers have the advantage of blocking oxygen from juices or other perishable foods, thereby preventing food spoilage and long term storage. Other advantages of the PC container are mentioned in light weight and high impact resistance.

However, the problem with the multilayer PC container is that, firstly, the apparent melt viscosity of the various layers is quite different at the extrusion temperature, which makes it difficult to carry out coextrusion blow molding therefrom, and the resin used as the second intermediate layer, for example, injects juice The glass transition temperature is not high enough to maintain the shape of the container during hot filling above 82 ° C. In addition, for example, when crystalline polyamide is used as the intermediate layer of the PC container, the transparency is lowered, thereby reducing the cleanliness of the product.

As described above, a multilayer container composed of various resin components has been proposed, but there is still a need for a satisfactory container having properties of heat resistance, gas barrier properties, and transparency.

Accordingly, the inventors have found that after extensive investigation and intensive research, the multilayer container composed of the unique amorphous polyester and / or derivative thereof and PC and / or derivative thereof exhibits excellent properties in heat resistance as well as gas barrier properties and transparency. To the present invention.

It is an object of the present invention to provide a multilayer structure laminate that can be used for food packaging applications.

Another object of the present invention is to provide a multilayer structure laminate that can be used in a container capable of storing food for a long time with excellent gas barriness.

It is another object of the present invention to provide a multilayer structure laminate suitable for a container having excellent transparency giving a visually clean feeling.

It is another object of the present invention to provide a multilayer structure laminate which can be used in a container which is excellent in heat resistance and suitable for high temperature filling.

According to the present invention, the above objects are oxygen scavenging of a composite resin and transition metal derivative system comprising 80 to 99% by weight of amorphous polyester resin having a crystallinity of less than 20% and 20 to 1% by weight of polyamide-based oxygen barrier resin At least one outer layer comprising 0.001 to 5% by weight of the composite resin, at least one intermediate layer mainly composed of polycarbonate resin, and 80 to 99% by weight of amorphous polyester resin having a crystallinity of less than 20% and polyamide-based oxygen At least one inner layer comprising up to 5% by weight of the composite resin and the transition metal derivative-based oxygen scavenger based on the barrier resin 20 to 1% by weight, the intermediate layer is the outer layer and the inner Located between the layers, the relative weight of the layers can be achieved by providing a gas barrier multilayer laminate that satisfies the following formula: The.

Where a is the weight per unit area of the outer layer, b is the weight per unit area of the intermediate layer, and c is the weight per unit area of the inner layer.

According to one aspect of the invention, the amorphous polyester resin of the outer layer and the inner layer may be the same or different from each other, to provide a gas barrier multi-layer laminate having a Tg in the range of 60 ℃ to 130 ℃.

According to another aspect of the invention, the intermediate layer comprises 50 to 70% by weight of a composite resin comprising 50 to 70% by weight of polycarbonate resin and less than 20% of amorphous polyester resin and polyamide-based oxygen barrier resin And a transition metal derivative-based oxygen scavenger up to 5% by weight relative to the total resin amount, wherein the polyamide-based oxygen barrier resin is present in an amount of 0.025 to 0.21% by weight of the total weight of the composite resin. Provided is a multilayer laminate.

According to another aspect of the present invention, the oxygen scavenger of the transition metal derivative system is composed of potassium sulfide, ascorbic acid derivative, cobalt (II) 2-ethylhexanoate and cobalt (II) neodecanoate. A gas barrier multi-layer laminate selected from the group is provided.

Thermoplastic polyester resins, in particular polyethylene terephthalate resins, which have excellent mechanical, gas barrier, chemical and hygienic properties, are now widely used in various containers and packaging materials in the form of films and sheets. With the development of blow molding technology, in particular biaxially stretch blow molding technology, these resins are frequently used for the production of hollow containers such as plastic bottles.

Plastic bottles, which have been used in a wide range of packaging products, such as soft drink beverages and mouthwash containers, are expected to grow further. For example, a container made of polyester resin, which is used for packaging various kinds of foods, reduces the exposure of food products to oxygen and thus has an effect of prolonging product life. For this reason, furthermore, plastic bottles have recently been in the spotlight as applications for alcoholic beverages.

In the present invention, a multilayer container having the advantages of polyester and polycarbonate using thermoplastic polyester resin as the outer and inner layers and PC resin as the intermediate layer is provided.

According to one embodiment of the invention, a gas barrier multi-layer laminate comprising at least one outer layer made of polyester resin, at least one intermediate layer made of polycarbonate resin, and at least one inner layer made of polyester resin To provide.

PET is widely used for container manufacture due to its excellent transparency and impact resistance. In addition, in certain applications, PET exhibits acceptable barrier properties against water vapor and gases.

PET is a crystalline polymeric material that can be in either an amorphous or crystallized state, or in a mixed state of both amorphous and crystalline states. When heated above its glass transition temperature and below its melting temperature, PET, even if not instantaneously, transitions from an amorphous state to a crystalline state. Similarly, when slowly cooled from the melting temperature to the glass transition temperature, the PET is crystallized, i.e., transitions from the amorphous state to the crystalline state. This transition does not take place immediately, and almost amorphous PET can be obtained by quickly quenching from the melt as disclosed in US Pat. No. 4,414,266.

This is because the crystallization that occurs when heating the polyester that can be crystallized is due to the growth of crystals present in the polymer, or the formation of new crystals, or both. Because of the increased level of crystallinity, many physical and chemical properties of polyester materials change. Various techniques are used to characterize the amount of crystallinity in the polymer. The degree of crystallinity can be observed, for example, directly by optical or electron microscopy techniques or estimated by refractive techniques.

The polyester resin used in the present invention is a resin in an amorphous state. Examples of polyesters that can be used include poly (ethylene terephthalate), poly (butylene terephthalate), poly (ethylene terephthalate / isophthalate), poly (ethylene glycol / cyclohexanedimethanol / terephthalate) Among these, amorphous polyethylene terephthalate (A-PET) is preferable.

Sheets made from A-PET ultimately excel in gloss and transparency in terms of product visuals. It also has excellent gas and moisture barrier properties, non-toxic and odorless. In addition, other excellent properties exhibited in A-PET include chemical resistance, oil resistance, toughness, stiffness, and impact strength.

In addition, A-PET is 100% renewable and environmentally friendly. Composed of carbon, hydrogen and oxygen, A-PET is completely burned during incineration, producing only water and carbon dioxide.

Thermal formability is also an indispensable property of A-PET, which, when sheeting, can be formed to a thickness in the range of 150-1,200 microns, vacuum forming, food and non-food packaging, folding and set-up boxes, It can be used in a wide range of applications, including stationery, printing and graphics.

The polycarbonate layer used in the present invention is located in the middle of the outer and inner layers, and is excellent in transparency and heat resistance. PCs that can be used are known in the art and are generally commercially available materials. PC resin can improve dihydric phenol and a carbonate precursor by an interfacial polymerization process. Generally, the dihydric phenols used are represented by following General formula (1).

In the above formula,

X is selected from a divalent hydrocarbon radical, -S-, -C (= 0)-, and-(O =) S (= 0),

Each R is independently selected from halogen radicals, monovalent hydrocarbon radicals, and monovalent hydrocarbonoxy radicals,

b is 0 or 1 and

n and n 'are independently an integer of 0-4.

In addition, the multilayer stack may further include an additive. Additives that can be used in addition to the polymer are known in the art and may be selected from stabilizers, antioxidants, ultraviolet absorbers, plasticizers, lubricants, colorants, fillers, and / or oxygen scavengers.

Examples of stabilizers include calcium acetate, calcium stearate, hydrotalcite, metal salts of ethylenediaminetetraacetic acid.

As antioxidant, 2, 5- di- t- butyl hydroquinone, 2, 6- di- t- butyl- p- cresol, 4, 4'- thiobis- (6- t- butylphenol), 2, 2 ' Methylene-bis (4'-methyl-6-t-butylphenol), octadecyl-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate, 4,4 '-Thiobis- (6-t-butylphenol) and the like can be used.

As the ultraviolet absorber, benzozinone, a triazine system and the like can be used.

Examples of plasticizers include dimethyl phthalate, diethyl phthalate, dioctyl phthalate, waxes, liquid paraffins, phosphoric acid esters, and the like.

Ethylenebisstearoamide or butyl stearate can be used as lubricant.

Colorants for imparting color to the container can be selected from carbon black, phthalocyanine, quiacridone, indolin, azo dyes, titanium dioxide, Indian red and the like.

Various fillers for enhancing physical properties can be used, such as glass fibers, asbestos, mica, ballastonite, sericite, talc, glass flakes, calcium silicate, aluminum silicate, calcium carbonate and the like.

It is known in the art to include oxygen scavengers in a package which, when used for packaging, react with and remove oxygen trapped in the package or permeated into the package. Oxygen scavengers that can be used in the present invention can use potassium sulfide, ascorbic acid derivatives, transition metal salts such as cobalt (II) 2-ethylhexanoate and cobalt (II) neodecanoate.

The laminate of the present invention can be produced using coextrusion molding techniques. For example, the laminate is formed using three extruders. Two of these extruders extrude amorphous PET resin while the other extrudes PC resin. When making hollow containers, three extruders can be used to extrude these three layers of parison and blow molding before solidification. Next, once solidified, the shape shown is almost unchanged to provide a multilayer container. Optionally two extruders can be used. One resin stream can be divided and used as inner and outer layers. In addition, the multilayer laminate of the present invention can also be made by a construction method.

Regarding the thickness, in the multilayer stack of the present invention, the minimum thickness of the amorphous polyester outer layer is primarily determined in consideration of its role as a gas barrier layer. This also depends to some extent on the intermediate layer used. However, the amorphous polyester outer layer is formed in a thickness range of 10 to 40%, preferably 20 to 35% of the total thickness of the multilayer stack. For example, when it is 10% or less, it may be poor in gas barrier properties and impact resistance, whereas when it is 40% or more, it is not preferable from a visual and economic point of view.

According to the invention, the thickness range of the amorphous polyester inner layer is between 10 and 40%, preferably between 20 and 35%, relative to the total thickness. For example, less than 10% may lead to poor results in gas barrier and chemical resistance, and more than 40% is undesirable from a visual and economic point of view as in the outer layer.

According to the invention, the PC is laminated in the thickness range of 20 to 40%, preferably 25 to 35%, in consideration of transparency and heat resistance. Forming thickness beyond the above range may expose problems in terms of transparency and heat resistance.

The minimum thickness of the laminates of the present invention lies in whether the laminates provide sufficient strength, stiffness, firmness and integrity to be used as effective containers for various materials, for example liquids, solids. Generally the minimum thickness of the laminate is about 0.25 millimeters and preferably about 0.8 millimeters. The maximum thickness is not a decisive factor but is determined by factors such as appearance, cost and weight. As a non-limiting example, when making a bottle, the thickness of the laminate can be about 30 to 70 millimeters.

Hereinafter, the present invention has been described in detail with reference to Examples and Comparative Examples, and the physical property results are shown in Table 1 below. The present invention was manufactured by 3-Layer multi-layer sheet using Japan's JSW (SHEET Extruder Maker) co-extrusion facility (L / D = 33, ㅨ = 113mm), the oxygen permeability of OX-TRAN 2/21 Was measured using.

Example 1

Nylon MXD6 (Mitsubishi Gas Chemical Co., Ltd.), which is a polyester resin and a polyamide oxygen barrier resin, is mixed at 92: 8% by weight, and 0.1 wt% of cobalt (II) 2-ethylhexanoate is used in comparison with the polymer. Extruded into an inner layer and an outer layer at 270 ° C., and as an intermediate layer, 60% by weight of a polycarbonate resin, 32% by weight of a polyester resin copolymerized with 1,4-dimethylcyclohexaol and 8% by weight of nylon MXD6. %, Cobalt (II) 2-ethylhexanoate was mixed 0.05 wt% relative to the interlayer polymer and coextruded into a 0.8 mm thick sheet at 280 ° C. combined with the outer layer. The coextruded sheet was fabricated in a 500 진공 container with a draw ratio of 300% using a vacuum molding machine, and oxygen permeability was measured. The heat resistance was evaluated by HDT using the method of ASTM D 648, and the optical characteristics were analyzed by ASTM D 1003. As a result of measuring the TT and haze, the physical property results are shown in Table 1.

Example 2.

In Example 1, the polyester-based resin was used 98% by weight of the inner layer and the outer layer and 38% by weight of the intermediate layer, and nylon MXD6 (Mitsubishi Gas Chemical Co., Ltd.), a polyamide-based oxygen barrier resin, was used as the inner layer, Except for changing to 2% by weight for both the outer layer and the intermediate layer was carried out in the same manner, the physical properties are shown in Table 1.

Example 3.

Except for using no cobalt (II) 2-ethylhexanoate in Example 1 and was carried out in the same manner, the physical properties are shown in Table 1.

Comparative Example 1.

In Example 1, nylon MXD6 (Mitsubishi Gas Chemical Co., Ltd.), a polyamide-based oxygen barrier resin, was added to the outer layer, the inner layer, and the intermediate layer, except that 100% polyester resin was used. , Physical property results are shown in Table 1.

Comparative Example 2.

Comparative Example 1 was carried out in the same manner, except that cobalt (II) 2-ethylhexanoate was not used, the physical properties are shown in Table 1.

Comparative Example 3.

Except that the polycarbonate-based resin used in the intermediate layer in Example 1 was replaced with the polyester-based resin was carried out in the same manner, the physical properties are shown in Table 1.

Table 1

division Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Copolymerization ratio Outer / inner layer PET / MXD6 92/8 98/2 92/8 100/0 100/0 92/8 Mezzanine PC / PET / MXD6 60/32/8 60/38/2 60/32/8 60/40 60/40 0/92/8 Scavenger Outer / inner layer 0.10wt% Left unused 0.10wt% unused 0.10wt% Mezzanine 0.05wt% Left unused 0.05wt% unused 0.05wt% Oxygen permeability (cc / pkg · day · atm) 0.002 0.008 0.400 25.0 31.0 0.001 Moisture permeability (g / ㎡ · day), 38 ± 2 ℃, 100% RH 1.0 1.1 6.5 15 18 0.8 Even after sheet 0.8mm Left Left Left Left Left Heat resistance (HDT) 108 ℃ 108 ℃ 108 ℃ 108 108 65 Transparency TT (Transmittance Rate) 90% 90% 90% 90% 90% 90% Haze 0.8% 0.7% 0.7% 0.8% 0.7% 0.8%

The sheet manufactured in the above experiments has better transparency and heat resistance and higher oxygen barrier properties than polyester resins of the same thickness, and can be used in packaging containers for various applications requiring the above physical properties. Compared with the use of ethylene (vinyl alcohol) copolymer resin, which is well known as a barrier resin, there is no process trouble to bring EVOH resin as a single layer, and it is coextruded with EVOH resin. The unique odors of polyolefin resins, ie, polypropylene and polyethylene resins, can be removed, and the price is competitive.

Claims (5)

80 to 99% by weight of amorphous polyester resin having a crystallinity of less than 20% and 20 to 1% by weight of polyamide-based oxygen barrier resin, and 0.001 to 5% by weight of oxygen scavenger of the transition metal derivative At least one outer layer, at least one intermediate layer mainly composed of polycarbonate resin, and 80 to 99% by weight of amorphous polyester resin having a crystallinity of less than 20% and 20 to 1% by weight of polyamide-based oxygen barrier resin, At least one inner layer containing up to 5% by weight of the oxygen scavenger of the transition metal derivative-based composite resin, the intermediate layer is located between the outer layer and the inner layer, the relative weight of the layer is A gas barrier multilayer multilayer that satisfies the requirements. Where a is the weight per unit area of the outer layer, b is the weight per unit area of the intermediate layer, and c is the weight per unit area of the inner layer. The gas barrier multi-layer laminate of claim 1, wherein the amorphous polyester resin of the outer layer and the inner layer may be the same or different from each other, and has a Tg in the range of 60 ° C to 130 ° C. The method of claim 1, wherein the intermediate layer comprises 50 to 70% by weight of a polycarbonate resin and 30 to 50% by weight of a composite resin comprising an amorphous polyester resin having a crystallinity of less than 20% and a polyamide-based oxygen barrier resin. A metal derivative-based oxygen scavenger comprises up to 5% by weight relative to the total resin amount, wherein the polyamide-based oxygen barrier resin is present in an amount of 0.025 to 0.21% by weight of the total weight of the composite resin. sieve. 2. The transition metal derivative based oxygen scavenger according to claim 1 is selected from the group consisting of potassium sulfide, ascorbic acid derivatives, cobalt (II) 2-ethylhexanoate and cobalt (II) neodecanoate. Gas barrier layered multilayer laminate. The gas barrier multilayer laminate of claim 1, wherein the outer layer comprises an additive selected from the group consisting of stabilizers, antioxidants, ultraviolet absorbers, plasticizers, lubricants, colorants, fillers, and mixtures thereof.