Molding material

Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing

Reexamination Certificate

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C428S035600, C428S903300, C524S013000, C524S014000

Reexamination Certificate

active

06495225

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a molding material for photosensitive photographic materials, which is mainly comprised of a vegetable fiber, exhibits good external appearance, emits no offensive odor, and does not cause any problem with fog formation during storage when employed as a container for photosensitive photographic materials.
BACKGROUND OF THE INVENTION
There are various types of molding materials employed for photosensitive materials. For instance, there are materials employed for imaging units such as cameras, and a body for lens-fitted film, resin canisters, cassettes for loading of rolled film strips, and the like.
These are molded, employing various materials in accordance with types, sizes, wound lengths, and uses of the employed photosensitive materials. Generally, however, said materials are divided into paper and plastics. In more detail, paper includes corrugated cardboard, paper board, laminated materials of paper with plastic film or metal foil, and the like. Molding materials for photosensitive materials, which are molded employing paper and/or plastics are required to be low cost and to cause no problems as waste when discarded or incinerated. Those which are molded employing paper cause no critical problem as waste. However, the strength is weak, and problems occur in which the size as well as wound length of photosensitive materials to be placed is limited and further critical problems occur in which during transportation, deformation an breakage tend to occur.
Those which are molded employing plastics exhibit high strength. However, problems occur in terms of cost as well as waste disposal. Those prepared by combining paper and plastics exhibit intermediate properties. However, problems also occur in disposal of combined plastic and paper materials when disposal requires separation the paper and plastics as waste, whereby, much labor is required.
As methods to overcome these problems, Japanese Patent Publication Open to Public Inspection No. 7-225453 proposes a light shielding container which is molded employing a mixture of a resin with a cellulose based fiber. However, when employing the molding materials described in the example, problems with external flatness and glossiness occur. In addition, it has been found that problems with the generation of offensive odor also result. Furthermore, it has been found that when it is used as a container for a photosensitive material, and said photosensitive material is stored in it over an extended period of time (for at least 6 months), problems occur in which photographic characteristics are adversely affected, and specifically, fog of said photosensitive material increases. Japanese Patent Publication Open to Public Inspection Nos. 61-225234 and 5-210217 also describe materials prepared by mixing a fiber with a thermoplastic resin. However it has been found that the same problems as described above occur.
An object of the present invention is to provide a molding material which exhibits excellent external appearance and emits no offensive odor, while overcoming the aforementioned problems. It is also an object to provide a molding material for photosensitive photographic materials, which gives no adverse effect on photographic performances, when employed as containers for photosensitive photographic materials. Another object is to provide a thermoplastic composition which exhibits excellent dimensional stability as well as excellent disposal properties as waste, even when employed in a thermoplastic composition comprising at least 50 percent of a cellulose based fiber.
Various shapes of molded products have been employed which employ molding methods such as injection molding, compression molding, injection-compression molding, extrusion molding, and the like, using a thermoplastic resin composition comprising a vegetable fiber as the main component. Such compositions are suitably employed for extrusion molding followed by machining, to produce, for example, base board and verandah, floor materials, handrails, materials in kitchens and bathrooms for house construction, materials for furniture, or board heartwood as interior finishing materials in cars. Wood flour filled vinyl chloride resins have been employed for similar uses. However, when said resins are employed, problems occur in which toxic gasses are generated during incineration in waste treatment, as well as during accidental fires.
Recently, the removal of vinyl chloride based compounds from waste has been demanded to overcome air pollution problems during incineration and the like, and materials which replace said compounds are urgently sought. Based on non-pollution, cost, ease of conversion, and the like, those which have received most attention are polyolefin resins such as polyethylene and polypropylene.
However, when a non-polar polyolefin resin is combined with a vegetable fiber with high polarity, it is technically difficult. to cause the resulting combination to exhibit features of each component as well as new functions. For example, vegetable materials such as wood flour and the like occasionally comprise, except for moisture, a large amount of components such as polysaccharides, lignin, tannin, and the like which tend to chemically and thermally undergo decomposition and deterioration. Though these can be removed, problems occur in which cellulose has no affinity with a polyolefin resin. In order to blend such components, a fairly large amount of energy is required. Due to that, after the completion of blending, the vegetable fiber as well as the resin is deteriorated.
Of conventional techniques, those in which a mixture consisting of a vegetable fiber and a thermoplastic resin in an amount of less than said vegetable fiber is employed, as the main component, include the following. Japanese Patent Publication Open to Public Inspection No. 54-72247 describes a method in which wood flour is subjected to thermal treatment at 160 to 260° C. in advance, and a processing aid, such as a thermoplastic resin, is added to the resulting wood flour, is allowed to melt and impregnate the wood flour, and said process is carried out at a relatively high temperature over a relatively long period to decrease the water content of said vegetable fiber. However, problems have occurred in which the strength decreases due to the deterioration of the components of the wood flour. Further, listed as processing aids of the resin are those having a melting point of 40 to 250° C. Of organic processing aids, some are not preferred due to low compatibility with polyethylene resin which results in a bleeding-out phenomenon and relatively large degradation of physical properties. Furthermore, Japanese Patent Publication Open to Public Inspection No. 63-112639 discloses a composition which is prepared by combining a polyolefin resin with mineral oil, synthetic oil and wax, an inorganic filler, or an organic filler comprising wood flour. However, when a mixture of mineral oil and synthetic oil, which tend to cause bleeding-out, is employed in molded parts, problems with external appearance have occurred. Japanese Patent Publication Open to Public Inspection No. 55-127451 discloses a composition comprised of polyolefin powder, and wood flour, calcium carbonate or talc. The use of polyolefin powder is a preferred method to improve hopper bridging as well as dispersibility. Furthermore, Japanese Patent Publication Open to Public Inspection No. 58-21755 discloses a composition prepared by combining polypropylene with wood flour as a lubricant. Listed as lubricants are higher alcohols and acid esters, as well as glycerin and fatty acid esters, and their functions are improvement in wettability of wood flour as well as polypropylene, enhancement of physical-properties and improvement in extrusion properties. Next, Japanese Patent Publication No. 58-56534 discloses a composition comprised of polyolefin resin and rosin or derivatives thereof, or petroleum resin, plasticizer and a vegetable fiber powder. A light shielding container for photosensitive

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