Layered silicate-containing composite resin composition, and moulded barrier composite resin

Abstract: To provide polyamide resin compositions exhibiting good gas barrier properties even during water adsorption, and moulded article thereof. Composite resin compositions as well as moulded articles thereof, comprising (A) 99.5 to 60 % by weight of aromatic polyamide resin or polyamide resin composition containing at least one aromatic polyamide resin, and (B) 0.5 to 40 % by weight of layered silicate modified by a triazine compound derivative having at least one positively charged group intercalated between its layers obtained by ion-exchange reaction with a triazine compound derivate; wherein the proportion of aromatic polyamide in the polyamide resin is at least 50 % by weight.

Description: Present invention relates to polyamide-based resin compositions with good gas barrier properties even during water absorption, and to the utilisation thereof. Polyamide resins have good heat resistance, gas barrier properties, transparency, oil resistance, shrinkability, and are broadly employed, e.g. for food packing material and automobile components. Recently, demands for a high degrees of food shelf stability, such as retort pouch treatment, have increased, and in particular demands for high gasbarrier properties, slidability, and tear strength under hight temperature conditions are required. However, the gas barrier properties of polyamide resins alone are not satisfying in comparison with ethylene-vinyl alcohol copolymers (EVOH), polyvinylidene chloride (PVDC), etc. Polyamide resins with better gas barrier properties are desirable. It is the purpose of the present invention to find a solution to the above, in particular to provide polyamide resin compositions with good gas barrier properties, hot water shrinkage, moulding shrinkage, slidability and tear strength, prepared by fine cleavage of layered silicates to disperse it in order to prepare polyamide resins good at said properties. Present inventors have diligently investigated above problem, and succeeded to obtain polyamide resin compositions with good gas barrier properties, good hot water shrinkage and good moulding shrinkage by the use of layered silicates subjected to a certain treatment with positively charged organic compounds, and completed the invention. In other words, the present invention relates to barrier composite resin compositions and moulded bodies, comprising (A) aromatic polyamide resins or polyamide resin compositions containing at least one aromatic polyamide resin, and (B) layered silicate modified by a triazine compound derivative. The invention is illustrated below. Aromatic polyamide resins employed in (A) aromatic polyamide resins or polyamide resin compositions containing at least one aromatic polyamide resin of the present invention, include polyamide resins with at least one aromatic ring at the backbone chain. They may be polyamide resins produced by polycondensation of aliphatic, cycloaliphatic, aromatic diamine compounds, such as hexamethylene diamine, decamethylene diamine, dodecamethylene, 2,2,4- or 2,4,4-trimethylhexamethylene diamine, 1,3- or 1,4-bis(aminomethyl)cyclohexane, bis(p-aminocyclohexyl)methane, m- or p-xylylene diamine and aliphatic, cycloaliphatic, aromatic dicarboxylic acid compounds, such as adipinic acid, suberic acid, sebacic acid, cyclohexane dicarboxylic acid, terephthalic acid, isophthalic acid, 1,3-phenylenedioxyzine acetic acid, or by polycondensation of or under addition of aminocarboxylic acid compounds, such as ε-aminocaproic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, lactam compounds, such as ε-caprolactam, enanthlactam, ω-laurolactam. Concrete examples are polyamide 6T, polyamide MXD6, polyamide 6I, and polyamide 6T/6I. Polyamide 6T, polyamide 6I and polyamide 6T/6I are preferable. Polyamide 6T is obtained by polycondensation of hexamethylene diamine and terephtalic acid (T), polyamide MXD6 by polycondensation of m-xylylene diamine (MXD) and adipinic acid and polyamide 6I by polycondensation of hexamethylene diamine and isophthalic acid (I). Polyamine 6T/6I is polyamide resin obtained by polycondensation of hexamethylene diamine and terephthalic acid (T) and hexamethylene diamine and isophthalic acid (I). One or many kinds of said aromatic polyamide resin may be employed; a mixture with any proportion of aliphatic polyamide resin, such as polyamide 6, polyamide 11, polyamide 12, polyamide 46, polyamide 66, polyamide 610, polyamide 612, is employable. If a higher gas barrier property is required, a proportion of aromatic polyamide resin in the polyamide resin composition of at least 50 % by weight is preferable. The manner of blending is not particularly limited to one method. Melt blending, solution blending and blending during polymerisation, etc. are exemplified. Layered silicate modified by a triazine compound derivative (B) of the present invention is obtainable by ion-exchange reaction of layered silicate and triazine compound derivatives. The layered silicate are classified as phyllosilicates in mineralogical terms, and in particular 2:1 phyllosilicates made of two tetrahedral layers and one octahedral layer, and 1:1 phyllosilicats made on one tetrahedral layer and one octahedral layer. Representative minerals for 2:1 phyllosilicates, are smectite, vermiculite, mica, chlorites, and for 1:1 phyllosilicate, kaolin, serpentine, etc. In the smectite group there are saponite, hectorite, sauconite, montmorillonite, beidellite, nontronite, stevensite, etc., in the vermiculite group, are trioctahedral vermiculite, dioctrahedral vermiculite, etc., in the mica group, there are compositions, such as phlogopite, biotite, lepidlite, muscovite, paragonite, chlorite, margarite, taeniolite, tetrasilicic mica, etc. Those phyllosilicates may be natural products, or synthetic ones produced by the hydrothermal method, melting method, solid phase method, etc. The triazine compound derivatives are reaction products of triazine compounds and Lewis acids. Triazine compounds are compounds with a six-membered ring containing 3 nitrogen atoms; for example melamine compounds, cyanuric acid compounds, and melamine cyanurate compounds, etc. Melamine compounds are compounds of the following chemical formula. In the formula R 1 and R 2 which may be the same or different stand for hydrogen atom, methyl group, ethyl group, methylene group, ethylene group, phenyl group, benzyl group or halogenophenyl group, etc. As concrete example of melamine compounds, there are melamine N-ethylene melamine, or N,N',N''-triphenyl melamine, etc. Cyanuric acid compounds are those of the following chemical formulae. In the formulae, R 3 which may be the same or different stand for hydrogen atom or lower alkyl group. In the present invention, hydrogen atom is preferable. As concrete example of cyanuric acid compounds, there are cyanuric acid, isocyanuric acid, trimethylcyanurate, trismethylisocyanurate, triethylcyanurate, trisethylisocyanurate, tri(n-propyl)cyanurate, tris(n-propyl)isocyanurate, diethylcyanurate, N,N'-diethylisocyanurate, methylcyanurate, methylisocyanurate, etc. Melamine cyanurate compounds are equivalent mol reaction products of melamine compounds and cyanuric acid compounds. They can, for instance, be produced by mixing and aqueous solution of melamine and an aqueous solution of cyanuric acid, the mixture is stirred at a temperature of ca. 90 to 100 °C. The generated precipitate is filtered of. This product is white solid, and is crushed into fine powder for use. Alternatively, commercial product, which may be used as it is or in crushed form, is employable. Lewis acid compounds are electron pair acceptors. Examples are hydrogenic acids, such as hydrochloric acid, hydrogen sulfide, etc., oxoacids, such as sulphuric acid, nitric acid, acetic acid and phosphoric acid; thioacids, such as ethylxantogen acid, etc., alkyl halide, acid halides. The amount of Lewis acid employed is normally 0.01 to 3 mol vis-à-vis mol of triazine compounds, and more preferably 0.1 to 2 mol. Methods for mixing said layered silicates and triazine compound derivatives to obtain the present layered silicate modified by a triazine compound derivatives are not particularly limited. For instance, there are methods of bringing them into contact via a medium with affinity to both, layered silicates and triazine compound derivatives, and methods of directly mixing them without the use of a medium. For the case where a medium is used, methods are exemplified wherein components are dispersed in the solvent to homogenise them, subsequently mixed under stirring, and where the solvent is finally removed to obtain the product. For the case where the components are directly mixed, methods are exemplified wherein the both components are simultaneously put into a ball mill or a mortar, and crushed to provide the product. The incorporation amount of triazine compounds in the layered silicate modified by a triazine compound derivative is preferably 0.3 to 5 equivalent amount of cation exchange capacity (hereinafter designated as CEC) of the layered silicate, and the range of 0.5 to 2.0 equivalent is most preferable. With less than 0.3 equivalent of the incorporation amount, the dispersion of the intercalation compounds in the resin composition is reduced, whereas with 5 equivalent or more, it is feared that an excess amount of triazine compounds may cause poor appearance of moulded articles by bleeding out during moulding or deterioration of physical properties. Since the CEC of layered silicates varies depending on species, places of production, compositions, etc., the CEC must be previously determined. Known measurement methods for the CECs, are, for instance, the column permeation method (refer to "Nendo Handbook" second version, edited by Nihon Nendogakkai, pp. 576-577, published by Gihohdoh Shuppan), the methylene blue absorption method (Nihon Bentonite Kogyokai standar test method, JBAS-107-91) and so on. To confirm the inclusion of triazine compounds in layered silicate modified by triazine compound derivative, a sample is subjected to powder X-ray diffraction (XRD) and thermogravimetric analysis (TG/DTA), wherefrom inclusion can be deduced. Bottom surface interval distance d (001) is increased by inclatrated triazine compounds. The amount of layered silicate modified by a triazine compound derivative contained in polyamide resin is 0.5 to 40 % by weight, in particular 1 to 10 % by weight is preferable. With less than 0.5 % by weight, improvement of gas barrier property, mechanical strength and heat resistance is poor; whereas with amount exceeding 40 % by weight, moulding property may be less favourable. Joining of layered silicate modified by a triazine compound derivative and polyamide resin, may be achieved by bringing the silicate into the polymerisation location during polymerisation of the polyamide resin or by kneading polyamide resin and the silicate within a melt kneading device, and so on. Example of the melt kneading device, are continuous mixer, Bunbary mixer, roll, single extruder, twin extruder, tandem-type extruder, etc. The gas barrier property of the moulded composite resin of the present invention is not limited to a certain shape, e.g. film, sheet, bottle, tank, etc., suitable for the utilisation purpose requiring gas barrier property. It is possible to laminate the present moulded resin together with other thermoplastic resins, such as polyethylene, polypropylene, acid anhydride etc. -graft modified ethylene/α-olefin copolymer polyolefines, polyvinyl chloride, ionomer resin, polyester resin, etc. Hereinafter examples of the present invention are given. The present invention however is not limited to these examples. As polyamide resin, aromatic polyamide 6I/6T (6I/6T - 7/3, hereinafter designated as "PA-1") with a relative viscosity of 2.7, polyamide 6 with a relative viscosity of 2.6 (hereinafter "PA-2") and polyamide 12 with a relative viscosity of 2.4 (hereinafter "PA-3) were employed. Layered silicate modified by a triazine compound derivative were prepared by the following methods: "SC-1": 200 g of synthetic sodium tetrasilic mica (ion exchange capacity: 107 meq/100 g; "SOMASIF ME-100" manufactured by Coop Chemical K.K.) were mixed with 4000 cc of distilled water and sufficiently swelled. This dispersion was heated to 60 °C, an aqueous melamine chloride solution of 60 °C was added thereto in an amount of 1.0 equivalent relative to ion exchange capacity of the layered silicate, the mixture was sufficiently stirred to effect ion exchange reaction. The suspension was filtered; washing and filtration were repeated; and drying and crushing were conducted to provide layered silicate modified by a triazine compound derivate. The distance between layers of the obtained layered silicate modified by a triazine compound derivate was 1.3 nm, and cyanuric acid derivate content was 10 % by weight. "SC-2": In the same manner as above, layered silicate modified by a triazine compound derivative was prepared from 200 g of synthetic sodium tetrasilicon mica, cynuric acid (160 mmol) and hydrochloric acid. The distance between layers of the obtained layered silicate modified by a triazine compound derivative was 1.3 nm, and cyanuric acid derivative content was 15 % by weight. For comparison, talc (average particle size D50 = 2.0 µm; 5000SA manufactured by Hayashi Kasei K.K.) was employed. In line with ASTM D3985, an oxygen permeation rate was measured by MOCON 0 X-TRAN 100A manufactured by Modern Control. The measurement condition was 23 °C, 50 % RH and 90 % RH. Components were blended in amounts shown in Table 1, and the mixture was melted and kneaded by a twin extruder (PCM30 manufactured by K.K. Ikegai) to provide pellets of composite resin composition. Obtained pellets were moulded into film by T-dieing at 240 °C in an extruder, the film was solidified on a roll of 90 °C to form a film of 40 µm thickness. Evaluation result was indicated in Table 1. Since the present composite resin composition composed of polyamide resin containing at least one aromatic polyamide and layered silicate modified by a triazine compound derivates exhibit good gas barrier properties, and is suitable for moulded articles requiring good gas barrier properties.

Claims: Barrier composite resin comprising (A) polyamide resin composition containing at least 50 % by weight or more of aromatic polyamide resin, and (B) triazine-modified layered silicate obtained by an ion exchange reaction between the silicate layers with a triazine compound derivate having at least one group with positive charge. Barrier composite resin according to claim 1 containing 0.5 to 40 % by weight of triazine-modified layered silicate (B).

Inventors: EBATA TSUGUO, INOUE HIROFUMI, NAKAMURA JUNICHI, NOGUCHI MASAYUKI, TAMURA KENJI, EBATA, TSUGUO, INOUE, HIROFUMI, NAKAMURA, JUNICHI, NOGUCHI, MASAYUKI, TAMURA, KENJI, Ebata, Tsuguo, c/o Showa Denko K. K., Inoue, Hirofumi, c/o Showa Denko K. K., Nakamura, Junichi, c/o Showa Denko K. K., Noguchi, Masayuki, c/o Showa Denko K. K., Tamura, Kenji, c/o Showa Denko K. K.
Applicants: EMS CHEMIE AG
Application year: 2000
Main classification: C08K9
IPC codes: C08K5, C08K9, C08L77, C08K3