Vessel for aerosol

Abstract: A vessel (1) according to the invention has a double-layer structure in which a vessel wall is constructed so as to have an inner layer (1b) made of a special high-nitrile resin having excellent chemical resistance, gas barrier properties and the like; and an outer layer (1a) made of a synthetic resin having excellent heat resistance, shock resistance, and the like. The vessel is suitable for use as a vessel for aerosol.

Description: The present invention relates to a vessel for aerosol made of a synthetic resin and, more particularly, to a vessel for aerosol made of a synthetic resin having excellent pressure resistance, heat resistance, and chemical resistance etc. Hitherto, vessels for aerosols have been made of metals such as tinplate, aluminum, or the like. In recent years, vessels for aerosols made from a synthetic resin have been used and synthetic resins comprising polyesters or polyacrylonitriles have been used as a raw material. Since the ultrasonic melt-bonding property of vessels made of polyester is poor, vessels in which a cap member made of metal is attached to an opening portion of the vessel have mainly been used. On the other hand, since high-nitrile resin has excellent ultrasonic melt-bonding properties, gas tightness, chemical resistance, and the like, it can preferably be used for vessels for aerosol and a pressure vessel which is suitable for actual use may thus be obtained. In such a conventional vessel for aerosol made of a synthetic resin, it is desirable that, for safety purposes, the vessel has pressure resistance even at high temperatures of 60 to 70°C or higher. In the case where the vessel main body is enlarged so as to increase its capacity, it is necessary, in order to ensure the required pressure resistance, to increase the thickness of the vessel wall or to provide a partition wall within the vessel. However, there exists the problem that as the thickness of the vessel wall is increased or a partition wall is provided within the vessel, the inner volume of the vessel ie. the capacity, is rendered smaller compared with the external volume. Consequently the capacities of aerosol vessels formed from synthetic resins tend to be smaller compared to the metal vessels of equivalent external volume. The present inventors have investigated the above problems and have found that it is possible to obtain a vessel for aerosols whose inner volume (compared with the external volume) is as large as possible and which has excellent pressure resistance, heat resistance and chemical resistance. The present invention commences from EP-A-0,221,563 which discloses a vessel for aerosols in which a vessel main body is made of synthetic resin and a spray valve assembly is made of a synthetic resin, the valve assembly being melt-bonded to an opening portion of the vessel main body and airtightly integral therewith. The invention is characterised in that the vessel main body has a double-layer structure and in that an inner layer of the vessel main body is made of a high-nitrile resin. Preferably, a main part of the valve assembly is also made of a high-nitrile resin. The high nitrile resin which is used in the present invention is a copolymer mainly containing an unsaturated nitrile compound such as acrylonitrile, methacrylonitrile, or the like and containing 50 weight % or more, preferably 55 weight % or more, of an unsaturated nitrile compound unit. As a comonomer, an unsaturated compound which is copolymerizable with the nitrile compound can be used. For instance, an unsaturated aromatic compound, a diene compound, an unsaturated ester, an unsaturated ether compound, or the like can be utilized. More specifically speaking, styrene, α-methystyrene, butadiene, isoprene, methylacrylate, ethylacrylate, methylmethacrylate, ethylmethacrylate, and the like can be utilized. At least one of them may be copolymerized with an unsaturated nitrile compound. On the other hand, as a high-nitrile resin, there can be mentioned a resin in which a rubber-like copolymer such as a butadiene-acrylonitrile copolymer, a butadiene-styrene copolymer, an isoprene-styrene copolymer, polybutadiene, polyisoprene, or the like has been mixed with the abovementioned copolymer in such a manner that the unsaturated nitrile unit content is 50 weight % or more. Particularly, there can be also mentioned a resin in which a mixture of an unsaturated nitrile compound and the abovementioned comonomer has been copolymerized in the presence of the aforesaid rubber-like copolymers. The abovementioned high-nitrile resins are preferable because of their shock resistance. Further, as a high-nitrile resin, a copolymer of an unsaturated nitrile compund with the above comonomer is used as a matrix and it is also possible to use a mixture of such a matrix and the foregoing rubber-like copolymer having a grafted portion of a composition similar to such a matrix or a grafted portion which is soluble in such a matrix. On the other hand, as a particularly desirable resin, there can be used a polymer in which 60 to 90 parts by weight of a monomer mixture comprising at least 60 weight % of an unsaturated nitrile compound and at least 5 weight % of an aromatic vinyl compound has been graft polymerized with 1 to 40 parts by weight of diene synthetic rubbers containing 50 weight % or more of a conjugated diene monomer, wherein in the above polymer, when it is assumed that a content of the unsaturated nitrile compound in the resin grafted to the rubbers is set to X weight % and a content of the unsaturated nitrile compound in the matrix resin is set to Y weight %, the following formula is satisfied between X and Y. 60 < X ≦ Y < 90 Generally, since the high-nitrile resin has a high environmental stress crack resistance, it is suitable for use in vessels for aerosol or the like which are subject to internal pressure stress and is widely used. However, the abovementioned special high-nitrile resin has an especially high environmental stress crack resistance and is suitable for such use. That is, a critical strain of the high-nitrile resin to ethanol which is used in vessels for cosmetics which have widely been used is about 0.4 to 1% as a value measured by a well-known Bergen's ¼ ellipse law. However, in the case of the above special high-nitrile resin, the critical strain of the high value of 0.65% or more is obtained. Therefore, vessels for aerosol having a further excellent durability can be obtained by using the above resins and the vessel thickness can be reduced. A oxidation inhibitor, and ultraviolet absorbent, an antistatic agent, a lubricant, a mineral filler agent, a color pigment, or the like, or small quantities of other resins may be also contained in the abovementioned high-nitrile resins. As a method of manufacturing the vessel main body of the double structure of the present invention, there can be used methods such as multilayer blow molding, multilayer injection-blow molding, multilayer injection molding, and the like. It is possible to mold and manufacture not only a cylindrical vessel but also vessels having various cross sectional shapes, for example in the form of an ellipse, a rectangle, and the like. A method in which, after the inner layer has been injection molded, the outer layer is injection molded thereby to obtain a double-layer molded article, (a double injection molding method) is suitable. On the other hand, in order to increase an inner layer adhesive property, an adhesive layer may be also provided between the outer and inner layers. The nature of the synthetic resin forming the outer layer of the vessel main body is not particularly limited. However, it is preferable to use a synthetic resin having excellent heat resistance, shock resistance etc.. As such synthetic resins, there can be mentioned polypropylene, acrylonitrile-styrene copolymer, acrylonitrile-styrene-butadiene copolymer, high-impact polystyrene, nylon, polyacetal, polycarbonate and the like. An inorganic mineral filler such as calcium carbonate, talc, barium sulfate, or the like, or glass fibers, carbon fibers and the like may be also contained in those resins. The cap member portion of the vessel of the invention is made of a high-nitrile resin. An integral airtight vessel may be obtained by melting and bonding the cap member and the inner layer portion of the vessel main body made of the high-nitrile resin to each other. As a method of melting and bonding the cap member and the container main body to each other, an ultrasonic melt-bonding method, a high frequency melt-bonding method, a spin welding method, and the like can be utilized. The vessels according to the present invention are useful as vessels for aerosol for storing a solution containing a solvent such as water, ethanol or the like for cosmetics, toiletry supplies, medicines, automobile supplies, industrial supplies, insecticide, germicide, antiphlogistic, hair conditioning agent, cleaners, and the like. Further, the above vessels are also suitable to store acid and alkaline solutions which could not be used in metal cans hitherto. The above vessels can be used to store a liquid of a pH value within a range from 2 to 13. Brief Description of the Drawing The drawing is a cross sectional view showing an embodiment of a vessel for aerosol according to the present invention. Preferred Embodiments of the Invention An embodiment of a vessel for aerosol according to the present invention will be described hereinbelow with reference to the drawing. Fig. 1 is a schematic cross sectional view of the vessel for aerosol of the invention. The vessel main body 1 comprises an outer layer 1b and an inner layer 1a. The vessel is formed by melt-bonding the inner layer 1a and a housing 3 to each other and then airtightly integrating them. In Fig. 1, the reference numeral 1 denotes a vessel and 2 indicates a spray valve assembly. The spray valve assembly 2 comprises: a housing 3; a valve 4; a spring 5; a packing 6; a sealing member 7; a pushing button 8; a nozzle 9; and a tube 10. In the present invention, the vessel main body 1 is formed as a double structure comprising an outer layer 1b and an inner layer 1a. The inner layer 1a and the housing 3, are manufactured by using a high-nitrile resin having excellent chemical resistance and gas barrier properties, thereby preventing loss of the contents through the wall of the vessel 1. On the other hand, desired characteristics of the vessel such as heat resistance, shock resistance and the like which cannot be provided solely by a high-nitrile resin may be ensured by forming the outer layer 1b of the vessel main body from a resin having excellent heat resistance, shock resistance, and the like. Although the thicknesses of the outer layer 1b and the inner layer 1a are not particularly limited, from the viewpoint of the resin properties, its processability and the ease of the melt-bonding process, and the like, typically the thickness of the outer layer 1b is set to a value within a range from 0.5 to 2.5mm, preferably 0.8 to 1.5mm, and the thickness of the inner layer is set to a value within a range from 0.5 to 2mm, preferably 0.8 to 1.5mm. The invention will now be described in more detail hereinbelow with reference to the examples which are presented by way of illustration only and do not limit the scope of the invention. Example 1 Monomer compositions of 100 weight parts comprising acrylonitrile (75 parts by weight) and methyl acrylate (25 parts by weight) were polymerized in the presence of 10 parts by weight of a butadiene-acrylonitrile rubber-like copolymer (butadiene content of 70 weight %), so that a high-nitrile resin (content ratio of acrylonitrile by nitrogen analysis is set to 70 weight %) was obtained. By use of the above high-nitrile resin and the nylon 66 (Amiran ®CM3, 001N - made by Toray Industries, Ltd.), a vessel main body whose inner layer is made of the high-nitrile resin and whose outer layer is made of nylon was obtained by using an injection molding apparatus suitable for molding a double-layer, the apparatus being made by Nissei Resin Industries, Ltd. In the central portion of the vessel thus obtained, the width was about 3.5cm, the thickness was about 3cm, the cross section was of a rectangular shape, the height was about 10cm, and the inner volume was about 75cc. The thickness of the outer layer was set to about 1.2mm and the thickness of the inner layer was set to about 1mm. A cap member was obtained by injection molding by using the above high-nitrile resin. A mixture of 50% (w/w) water and 50% (w/w) ethanol was poured into the vessel main body. The cap member to which the parts of the spray apparatus had been assembled was melted and bonded and sealed to the vessel main body by ultrasonic welding while maintaining an inner pressure of 3.5kg/cm² with a gaseous mixture of Freon® 11 and Freon® 12. Ten vessels were prepared as mentioned above and left at 65°C for 24 hours and were then examined for the presence or absence of deformation. No deformation was found in any of the vessels. A further ten vessels were also similarly manufactured. These ten vessels were subjected to repetitive drop tests at room temperature by dropping them 30 times from a height of 1.2m onto a plastics tiled floor. No damage was found in any of the vessels. Example 2 Monmomer compositions (100 parts by weight) comprising acrylonitrile (80 parts by weight), methyl acrylate (5 parts by weight), and styrene (15 parts by weight) were polymerized in the presence of 8 parts by weight of a butadiene-acrylonitrile rubber-like copolymer (butadiene content 70 weight %), so that a high-nitrile resin (acrylonitrile content by nitrogen analysis was 73 weight %) was obtained. A vessel was molded in a manner similar to Example 1 except that such a high-nitrile resin was used for the inner layer of the vessel main body and polyacetal (Juracon® M140 - made by Polyplastics Co., Ltd.) was used for the outer layer of the vessel main body. The vessel was filled, sealed and tested in the manner described in Example 1. The result of the tests showed that no deformation or damage of the vessels occurred. Comparison 1 Vessels of the shape similar to that in Example 1 were molded except that only the high-nitrile resin was used. Tests similar to those in Example 1 were then performed. The results of the tests showed that although no leakage of the contents was observed, a clear deformation was found in all ten vessels. In the drop test, damage was found to occur during the 20th to 28th tests in three of the ten vessels. Example 3 A mixture comprising acrylonitrile (65 parts by weight), styrene (20 parts by weight) and methyl methacrylate (15 parts by weight) was polymerized in the presence of 10 parts by weight of a butadiene-acrylonitrile rubber-like copolymer (butadiene content 62 weight %), so that a high-nitrile resin was obtained. A vessel for aerosol was formed in a manner similar to Example 1 except that the above high-nitrile resin was used. Tests similar to those in Example 1 were executed. Results of the tests showed that no abnormalities were found in any of the ten vessels. Example 4 Ethanol and a spray agent were sealed into the same vessels as those used in Examples 1, 2 and 3 in a manner such that an inner pressure was set to about 5kg/cm³. This pressure is higher than that of the ordinary aerosol. Twenty vessels were manufactured with respect to each of Examples 1 to 3. Each ten vessels were held at 55°C and 60°C for one week respectively. After that, the vessels were disassembled and the states of the inner surfaces were examined. With respect to the same vessels as those in Examples 1 and 2, no abnormalities were found at both of the test temperatures. However, with regard to the same vessels as those used in Example 3, although no abnormalities were found at a test temperature of 55°C; in the case of 60°C, small cracks were found in the ultrasonic melt-bonded portions in six of the ten samples. Sheets each having a thickness of 1mm were manufactured using the abovementioned resins and the critical strain to ethanol was measured by Bergen's ¼ ellipse law. Thus the critical strain values obtained were 0.68%, 0.75% and 0.57% respectively. The above three-kinds of high-nitrile resins were respectively dissolved in a solvent mixture containing dimethylformamide and acetonitrile in a ratio of 1:1, thereby separating them into a graft portion which is insoluble in the solvent and a matrix portion which is soluble in the solvent. The acrylonitrile contents of the resins were examined. In the resins of Examples 1 to 3, the acrylonitrile contents of the graft resins were 65 weight %, 76 weight %, and 78 weight % respectively and the acrylonitrile contents of the matrix resin were 73 weight %, 78 weight %, and 58 weight % respectively. Example 5 Monomer compositions (100 parts by weight) comprising acrylonitrile (75 parts by weight) and methyl acrylate (25 parts by weight) were polymerized in the presence of 10 parts by weight of a butadieneacrylonitrile rubber-like copolymer (butadiene content of 70 weight %) so that a high-nitrile resin (acrylonitrile content by nitrogen analysis is set to 70 weight %), was obtained. By use of the abovementioned high-nitrile resin and a polycarbonate [Panlight® L-1225L (made by Teizin-Kasei Co. Ltd.)], a vessel main body whose inner layer is made of the high-nitrile resin and whose outer layer is made of polycarbonate was obtained by using an injection molding apparatus suitable for molding a double-layer, the apparatus being made by Nissei Resin Industries, Ltd. In the central portion of the vessel thus obtained, the width was about 3.5cm, the thickness was about 3cm, the cross section was of a rectangular shape, the height was about 10cm, and the inner volume was about 75cc. On the other hand, the thickness of the outer layer was set to about 1.2mm and the thickness of the inner layer was set to about 1mm. A cap member was obtained by injection molding by using the abovementioned high-nitrile resin. A mixture of water (50%w/w) and ethanol (50% w/w) was poured into the vessel main body. The cap member to which the parts of the spray apparatus had been assembled was melted and bonded and sealed to the vessel main body by ultrasonic welding while maintaining an inner preseure of 2.5kg/cm² with LPG (liquid petroleum gas). Ten vessels were prepared as mentioned above and left at 550°C (which temperature corresponds to the test temperature for gas-lighters made of organic resins) for one month and were then examined for the presence or absence of deformation. However, the maximum deformation was less than 0.5mm at the middle part of the vessel body in all of the vessels. After said test, each of the vessels was cut and the status of the inner surface was examined. No abnormalities such as cracks were found. A further ten vessels were also similarly manufactured. Those vessels were subjected to repetitive drop tests at room temperature by dropping them 30 times from a height of 1.2m onto the plastics tiled floor. No damage was found in any of the vessels. Industrial Applicability Vessels for aerosol of the present invention have excellent chemical resistance, gas barrier properties, and the like and can be advantageously used as vessels for aerosol because the vessel main body has a double-layer structure and the inner layer is made of a high-nitrile resin. The vessels of the invention have excellent heat resistance, shock resistance, and the like because the outer layer is made of a synthetic resin having excellent heat resistance, shock resistance, and the like. Further, there is no need to provide a partition wall in the vessels in order to maintain pressure resistance, so that the inner volume is not reduced.

Claims: A vessel for aerosol comprising a vessel main body (1) made of a synthetic resin and a spray valve assembly (2) made of a synthetic resin, the valve assembly (2) being melt-bonded to an opening portion of the vessel main body (1) and airtightly integral therewith, characterised in that the vessel main body (1) has a double-layer structure (1a, 1b), and in that an inner layer (1a) of the vessel main body is made of a high-nitrile resin. A vessel according to claim 1, wherein a main part (3) of the spray valve assembly (2) is made of a high-nitrile resin. A vessel according to claim 1, wherein the vessel main body (1) has a cylindrical shape. A vessel according to claim 1, wherein the vessel main body (1) has a rectangular pipe shape. A vessel according to claim 1, wherein the vessel main body (1) has an elliptical pipe shape.

Inventors: AMEMIYA HIDEO, KURODA MINORU, NITTA TOMIO, AMEMIYA, HIDEO, KURODA, MINORU, NITTA, TOMIO
Applicants: MITSUI TOATSU CHEMICALS, TOKAI CORP, KABUSHIKI GAISHA TOKAI, MITSUI TOATSU CHEMICALS, INC.
Application year: 1990
Main classification: B65D83
IPC codes: B65D83