Oxygen absorbent

Abstract: The present invention relates to novel oxygen absorbent comprising as a main ingredient a 1,2-glycol, glycerine or sugar alcohol.

Description: The present invention relates to oxygen absorbents. The term "oxygen absorbent" as used throughout the specification refers primarily to a "composition having an oxygen absorbing action" (oxygen absorbent composition) but is sometimes used to mean "package of a composition having an oxygen absorbing action". As a technique for preservation of, e.g., foodstuffs, oxygen absorbents are used. This technique is used to prevent oxidation of foodstuffs and, for example, growth and proliferation of bacteria or mildew by allowing foodstuffs and oxygen absorbents to be present in a sealed bag or sealed container having gas barrier properties (hereafter sometimes simply referred to as a "sealed container" or a "container") to thereby render the sealed system substantially an oxygen-free state. The technique has been widely used for, e.g., the preservation of foodstuffs. Oxygen absorbents mainly composed of iron powders have been hitherto used, e.g., because of their ability of absorbing oxygen, easy handling, safety and costs. In the case of, for example, packaged food, the package is applied to a metal detector after sealing food in a packaging bag to examine if it is contaminated with foreign matters. However, oxygen absorbents mainly composed of iron powders are detected with the metal detector, as a matter of course. It was thus impossible to apply a metal detector to packaged food sealed together with oxygen absorbents. In view of the problem involved in the prior art, an object of the present invention is to provide oxygen absorbents which are not detected with a metal detector. JP-A-56111042 discloses an oxygen absorbent consisting of iron powder, metallic halide, carbonaceous material, water and calcined vermiculite as water-holding agent to improve the safety and packaging workability of the oxygen absorbent. Optionally, a compound containing a hydroxyl group, for example, ethylene glycol, may be incorporated in order to suppress the evolution of hydrogen gas. JP-A-5281085 relates to an oxygen absorbent absorbing oxygen at a high rate and which is easy to handle, comprising 100 parts by weight of sulfites of at least one alkaline earth metal, 0.1 parts by weight of salts of transition metals, except for ferrous salts and aluminium salts, and 2 to 200 parts by weight of free water. The oxygen absorbent is used for preservation of foods, moth and mildew proofing of garments, the prevention of corrosion of metals and the prevention of a change of properties of chemical products. JP-A-56121634 decribes an oxygen absorbent for addition into sealed packages of food, etc, which is obtained by coating a metal halide, such as sodium chloride, on a filler, such as zeolite or active carbon, and drying the filler or coating said filler with a metal halide and a binder, such as ethylene glycol, and subsequently mixing the coated filler with iron powder. According to the present invention the aforementioned object underlying the present invention is attained with an oxygen absorbent comprising an alkaline substance, a transition metal compound and either at least one 1,2-glycol, or at least one sugar alcohol, or glycerine. Preferred embodiments of the present oxygen absorbent are set forth in the dependent claims. The present invention covers the embodiments of: the aforesaid absorbent comprising a 1,2-glycol, an alkaline substance and a transition metal compound; and compositions obtained by further adding other components to the above compositions, depending upon necessity. Thus, the present invention includes, for example, (1) an oxygen absorbent comprising a 1,2-glycol, an alkaline substance and a transition metal compound; (2) an oxygen absorbent comprising a 1,2-glycol, an alkaline substance, a transition metal compound and water; (3) an oxygen absorbent comprising a 1,2-glycol, an alkaline substance, a transition metal compound and a solid which is sparingly soluble in water; (4) an oxygen absorbent comprising a 1,2-glycol, an alkaline substance, a transition metal compound, a solid which is sparingly soluble in water, and water. The present invention further comprises an oxygen absorbent comprising a 1,2-glycol, an alkaline substance, a phenolic compound or quinone compound and a transition metal compound; an oxygen absorbent comprising a 1,2-glycol, an alkaline substance, a phenolic compound or quinone compound, a transition metal compound and water; an oxygen absorbent comprising a 1,2-glycol, an alkaline substance, a phenolic compound or quinone compound, a transition metal compound and a solid which is sparingly soluble in water, an oxygen absorbent comprising a 1,2-glycol, an alkaline substance, a phenolic compound or quinone compound, a transition metal compound, a solid which is sparingly soluble in water and water; The present invention also provides an oxygen absorbent comprising glycerine, an alkaline substance and a transition metal compound; an oxygen absorbent comprising glycerine, an alkaline substance, a transition metal compound and water; an oxygen absorbent comprising glycerine, an alkaline substance, a transition metal compound and a solid which is sparingly soluble in water; an oxygen absorbent comprising glycerine, an alkaline substance, a transition metal compound, a solid which is sparingly soluble in water and water; oxygen absorbents obtained by further adding a phenolic compound or quinone compound to the oxygen absorbents described above. Further, the present invention comprises an oxygen absorbent comprising sugar alcohol, an alkaline substance and a transition metal compound; an oxygen absorbent comprising sugar alcohol, an alkaline substance, a transition metal compound and water; an oxygen absorbent comprising sugar alcohol, an alkaline substance, a transition metal compound and a solid which is sparingly soluble in water; an oxygen absorbent comprising sugar alcohol, an alkaline substance, a transition metal compound, a solid which is sparingly soluble in water and water; oxygen absorbents obtained by further adding a phenolic compound or quinone compound to the oxygen absorbents described above. In the embodiments described above, the 1,2-glycol may be one commercially available, may contain impurities such as water or may be a mixture. As the 1,2-glycol, for example, ethylene glycol, propylene glycol are preferred. Of these, propylene glycol is particularly preferred. Glycerine may be one commercially available or may contain impurities such as water. Sugar alcohol may be one commercially available, may contain impurities such as water or may be a mixture. As the sugar alcohol, there may be exemplified sugar alcohol having 4 carbon atoms, sugar alcohol having 5 carbon atoms or sugar alcohol having 6 carbon atoms. Specific examples include sugar alcohol having 4 carbon atoms, e.g., erythritol; sugar alcohol having 5 carbon atoms such as arabitol, xylitol and adonitol; and sugar alcohol having 6 carbon atoms such as mannitol, sorbitol and dulcitol. Xylitol, mannitol and sorbitol are preferred, with particular preference being sorbitol. The alkaline substance is a substance which reacts with water or dissolves in water to become alkaline. Hydroxides, carbonates, hydrogencarbonates, tertiary phosphates and secondary phosphates, for instance, of alkali metals or alkaline earth metals are preferred. Of these, hydroxides of alkali metals and alkaline earth metals are particularly preferred. Specific examples which are preferred include sodium hydroxide, sodium carbonate, sodium hydrogencarbonate, sodium tertiary phosphate, sodium secondary phosphate, potassium hydroxide, potassium carbonate, potassium hydrogencarbonate, potassium tertiary phosphate, potassium secondary phosphate, calcium hydroxide and magnesium hydroxide. Of these, sodium hydroxide, potassium hydroxide and calcium hydroxide are particularly preferred. The alkaline substance may be used singly or as admixture of two or more. An amount of the alkaline substance to be mixed with the 1,2-glycol, glycerine or sugar alcohol is preferably at least 10 parts (by weight, hereafter the same), more preferably 30 to 1,000 parts, based on 100 parts of the 1,2-glycol, glycerine or sugar alcohol. If the amount of the 1,2-glycol mixed was less than the lower limit described above, the amount of oxygen absorption in the composition would decrease undesirably. Conversely if the amount of the 1,2-glycol mixed exceeded the upper limit described above, the amount of oxygen absorption per unit weight would decrease so that it would be necessary to increase the size of the material for packaging the composition. This necessity results in inconvenience of food package in wrapping and also in undesirable appearance. In the present invention the transition metal compound is exemplified by halides, sulfates, nitrates, phosphates, carbonates, oxides, hydroxides, organic acid salts, other complexes and chelate compounds of transition metals. As transition metals in the transition metal compound, e.g., iron, cobalt, nickel, copper, zinc and manganese are used. Of these, copper, iron and manganese are preferred. Taking safety into account, iron is most preferred. Specific examples of the most preferred transition metal compound in the present invention include inorganic or organic iron compounds such as, for example, ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, ferrous hydroxide, ferric hydroxide, iron citrate, ferrous tartarate and ferric tartarate. When a sugar alcohol is present in the oxygen absorbent, e.g., ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, cuprous chloride, cupric chloride, cupric sulfate, cupric hydroxide, copper citrate, cuprous tartarate, cupric tartarate and manganese chloride are most preferred. These transition metal compounds are incorporated singly or as admixture of two or more, depending upon necessity. The transition metal compound acts as a catalyst of the absorbent of the present invention. The amount of the transition metal compound to be formulated is preferably 1 part or more particularly preferably 5 parts or more, based on 100 parts of the 1,2-glycol, glycerine or sugar alcohol. The phenolic compound exhibits a catalytic action in the present invention. Even if the phenolic compound is added in a small quantity, the rate of oxygen absorption can be increased. As the phenolic compound, a monovalent phenolic compound and a polyvalent phenolic compound of at least bivalency can be used. Any substituted phenols and aromatic derivatives having other substituents on the aromatic nucleus may be used as the monovalent phenolic compound as long as they contain one hydroxy group directly bound to the aromatic nucleus in one molecule. Any substituted phenols and aromatic derivatives having other substituents on the aromatic nucleus may be used as the divalent phenolic compound as long as they contain at least two hydroxy groups directly bound to the aromatic nucleus in one molecule. In the present invention, phenolic compounds having a plurality of aromatic nuclei in one molecule and containing a plurality of hydroxy groups directly bound to the aromatic nuclei are classified into polyvalent phenolic compounds, even though they have a single hydroxy group on a single aromatic nucleus. Of course, the phenolic compound may be a phenol salt (phenolate), for instance in which the hydrogen of the hydroxy group is substituted with a metal. Of these phenolic compounds, a polyvalent phenolic compound showing two or more valency is preferred because of their catalytic action. Specific examples of the polyvalent phenolic compound include catechol, resorcine, hydroquinone, pyrogallol, naphthohydroquinone, phloroglucine, gallic acid, tannin, tannic acid, dihydroxyphenylphenol, or derivatives thereof. Of these, polyvalent phenolic compounds such as catechol, resorcine, hydroquinone, pyrogallol, gallic acid, tannin and tannic acid are preferred in view of, e.g., their catalytic action on oxygen absorption rate and easy access. In the present invention, quinone compounds may also be used instead of the phenolic compounds. The quinone compounds also show a catalytic action resulting in an increased oxygen absorption rate by their addition even in a small quantity. As the quinone compounds, any of o-quinones and p-quinones may be used. The quinone compounds may be their derivatives having a substituent(s) on the quinone nucleus as long as they take a quinone structure. Specific examples include benzoquinone, naphthoquinone, phenanthraquinone and diphenoquinone or derivatives thereof. Of these, benzoquinone and diphenoquinone are preferred. The phenolic compound and the quinone compound may be used singly or as admixture of two or more, depending upon necessity. The amount of the phenolic compound or quinone compound formulated in the 1,2-glycol, glycerine or sugar alcohol is not particularly limited but is preferably at least one part, more preferably 5 parts or more, based on 100 parts of the 1,2-glycol, glycerine or sugar alcohol. When the amount is less than the lower limit described above, the catalytic effect of the phenolic compound or quinone compound is poor. The upper limit of the amount of the phenolic compound or quinone compound formulated in the 1,2-glycol, glycerine or sugar alcohol is not particularly limited. It is possible to formulate a catalytic amount or more of the phenolic compound or quinone compound but it is preferred to formulate less than 5,000 parts, particularly preferably less than 1,000 parts of the phenolic compound or quinone compound, based on 100 parts of the 1,2-glycol, glycerine or sugar alcohol. When the amount of the phenolic compound or quinone compound to be formulated exceeds the upper limit described above, it does not contribute to an increase in the oxygen absorption amount of the 1,2-glycol, glycerine or sugar alcohol proportional to an increase in compositional amount. Thus, the economical efficiency is poor. The solid which is sparingly soluble in water is a solid substance which is insoluble or difficult to dissolve in water. Specific examples include powders or particles of activated charcoal, zeolite, perlite, diatomaceous earth, active clay, silica, kaolin, talc, bentonite, activated alumina, gypsum, silica alumina, calcium silicate, magnesium oxide, black lead, carbon black, aluminum hydroxide and iron oxide. The solid which is sparingly soluble in water may be used singly or as admixture of two or more, depending upon necessity. By formulating the solid which is sparingly soluble in water, the oxygen absorption rate or an oxygen absorption amount can be increased and the handling of the composition can be simplified. Furthermore, the formulation of the solid which is sparingly soluble in water can increase the contact area of the liquid components in the composition with oxygen. The amount of the solid which is sparingly soluble in water may be appropriately chosen in relation to the other components but is not particularly limited. It is preferred to formulate the solid substance preferably in an amount of 0.1 to 10,000 parts, more preferably in an amount of 1 to 1,000 parts, based on 100 parts of the 1,2-glycol, glycerine or sugar alcohol. When no water is added to the absorbent composition, water required for the reaction is supplied from water evaporated from preserved matters such as, for example, food. When water is added to the oxygen absorbent composition, the oxygen absorbing reaction proceeds without relying on water from food, for instance, so that it is possible to regulate the progress of the oxygen absorbing reaction by the addition amount of water. In this case, the amount of water to be added is not particularly limited but it is desirably controlled to less than 70 wt%, more desirably less than 50 wt%, based on the total weight of the composition. When the amount of water added exceeds the above range, the resulting composition becomes a paste so that the contact area of the composition with oxygen becomes undesirably small. In the present invention, the method for mixing the respective components described above is not particularly limited. In the case that the components are liquid and powders, any method is applicable as long as these components can be uniformly mixed with each other. In the case of using particulate components, for example, a method in which the liquid is impregnated with particles and powders are then sprinkled over the impregnated particles may be adopted. The respective components described above are generally encased in an air-permeable packaging material to form a package. A method of packaging comprises, for example, mixing the respective components, and wrapping the mixture with a small bag sealed by heat-sealing the periphery of an air-permeable packaging material to thereby form an oxygen absorbent package. The oxygen absorbent package can be used to preserve, e.g., foodstuffs by encasing the oxygen absorbent together with food in an air-impermeable packaging material and sealing the same, or encasing the oxygen absorbent together with food in a sealed container and sealing the container. When no water is contained in the composition, the oxygen absorbent composition of the present invention can be applied to foodstuffs having a relatively large water content in which moisture evaporated from the foodstuffs is taken up into the composition to absorb oxygen. In particular, the 1,2-glycols such as, for example, ethylene glycol and propylene glycol or glycerine are extremely strongly hygroscopic or the sugar alcohol is hygroscopic so that the absorbent of the present invention displays a good oxygen absorbing function in an atmosphere with rapid evaporation of moisture. In this case, there is the advantage that handling is easy in sealing the oxygen absorbent together with foodstuffs. Furthermore, when water is incorporated in the absorbent composition, the oxygen absorbent can be used as an oxygen absorbent which can absorb oxygen, irrespective of the water content of the food. Examples 1 through 4 After the respective components for oxygen absorbents shown in Table 1 were mixed with each other, the oxygen absorbents were encased in a small bag (50 mm in length, 80 mm in width) prepared using a packaging material of paper laminated with perforated polyethylene, respectively, to prepare oxygen absorbent packages. The oxygen absorbent packages were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, respectively, together with 500 ml of air. After sealing, the bag was allowed to stand in an atmosphere of 25°C. After six days, the oxygen concentration in the bag was measured to determine the oxygen absorption amount. The results are shown in Table 1. In Examples 1 and 3, water-impregnated absorbent wadding was sealed in the bag together and the relative humidity was set at 100%. Example 1 Example 2 Example 3 Example 4 Amount formulated (unit, g): Propylene glycol 1 1 1 1 Calcium hydroxide 4.5 4.5 1 1 Water 0.6 Ferrous chloride 0.2 0.2 0.2 0.2 Activated charcoal 1 1 Amount of oxygen absorbed (ml) 19 20 58 83 Example 5 The procedure was repeated in a manner similar to Example 1 except that 5 g of propylene glycol, 5 g of calcium hydroxide, 1 g of manganese chloride, 5 g of activated charcoal and 5 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. An amount of oxygen absorbed was 103 ml in this case. Example 6 The procedure was repeated in a manner similar to Example 1 except that 5 g of ethylene glycol, 5 g of calcium hydroxide, 1 g of ferrous chloride, 5 g of activated charcoal and 5 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. The amount of oxygen absorbed was 103 ml in this case. Example 7 After 400 rice weevil imagines were fed in 1 kg of brown rice for a week, the imagines were removed. The remaining brown rice was divided into 20 g each and provided as samples for the following test. After 20 g of brown rice sample and the oxygen absorbent package of Example 5 were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, the bag was sealed to have an air amount in the bag of 500 ml. Ten specimens were prepared in a similar manner and stored in a thermostat at 20°C. After storing for 20 days, the bags were unsealed and allowed to stand at 25°C in the thermostat. The number of rice weevils that emerged from the brown rice sample was recorded. For control group, the same test was performed as described above except that the oxygen absorbent package was not enclosed in the bag. In this case, the number of rice weevils that emerged was made 100%. The results are shown in Table 2. Number of Rice Weevil Emerged Rate of Weevil Emerged Example 7 0 0% Control group 1,500 100% Example 8 After 5 bean jam-filled buns weighing 15 g each and the oxygen absorbent package of Example 6 were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, the bag was sealed to have an air amount in the bag of 500 ml and stored at 20°C. After one week, the oxygen concentration in the bag and the concentration of carbon dioxide gas were measured and the property of the buns was observed. For control group, the same test was performed as described above except that the oxygen absorbent package was not enclosed in the bag. The results are shown in Table 3. Concentration of Oxygen (%) Concentration of Carbon Dioxide (%) Property of Bean Jam-Filled Bun Example 8 0.01 0 No-abnormality was noted. Control group 16.4 3.6 Mildew generated. Examples 9 through 12 After the respective components for oxygen absorbents shown in Table 4 were mixed with each other, the oxygen absorbents were encased in a small bag (50 mm in length, 80 mm in width) prepared using a packaging material of paper laminated with perforated polyethylene, respectively, to prepare oxygen absorbent packages. The oxygen absorbent packages were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, respectively, together with 1,000 ml of air. After sealing, the bag was allowed to stand in an atmosphere of 25°C. After three days the oxygen concentration in the bag was measured to determine the oxygen absorption amount. The results are shown in Table 4. In Examples 9 and 11 water-impregnated absorbent wadding was sealed in the bag together and the relative humidity was set at 100%. Example 13 The procedure was repeated in a manner similar to Example 9 except that 5 g of propylene glycol, 5 g of calcium hydroxide, 1 g of hydroquinone, 1 g of ferrous chloride, 3 g of silica powders, 1 g of activated charcoal and 3 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. The amount of oxygen absorbed was 206 ml in this case. Example 14 The procedure was repeated in a manner similar to Example 9 except that 5 g of ethylene glycol, 5 g of calcium hydroxide, 1 g of catechol, 1 g of ferrous chloride, 5 g of activated charcoal and 5 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. The amount of oxygen absorbed was 206 ml in this case. Example 15 After 400 rice weevil imagines were fed in 1 kg of brown rice for a week, the imagines were removed. The remaining brown rice was divided into 40 g each and provided as samples for the following test. After 40 g of brown rice sample and the oxygen absorbent package of Example 9 were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, the bag was sealed to have an air amount in the bag of 1000 ml. Ten specimens were prepared in a similar manner and stored in a thermostat at 20°C. After storing for 20 days, the bags were unsealed and allowed to stand at 25°C in the thermostat. The number of rice weevils emerged from the brown rice sample was recorded. For control group, the same test was performed as described above except that the oxygen absorbent package was not enclosed in the bag. In this case, the number of rice weevils emerged was made 100%. The results are shown in Table 5. Number of Rice Weevil Emerged Rate of Weevil Emerged Example 15 0 0% Control group 1,500 100% Example 16 After 10 bean jam-filled buns weighing 15 g each and the oxygen absorbent package of Example 13 were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, the bag was sealed to have an air amount in the bag of 1000 ml and stored at 20°C. After one week the oxygen concentration in the bag and the concentration of carbon dioxide gas were measured and the property of the buns was observed. For control group, the same test was performed as described above except that the oxygen absorbent package was not enclosed in the bag. The results are shown in Table 6. Concentration of Oxygen (%) Concentration of Carbon Dioxide (%) Property of Bean Jam-Filled Bun Example 21 0.01 0 No-abnormality was noted. Control group 16.4 3.6 Mildew generated. Examples 17 through 20 After the respective components for oxygen absorbents shown in Table 7 were mixed with each other, the oxygen absorbents were encased in a small bag (50 mm in length, 80 mm in width) prepared using a packaging material of paper laminated with perforated polyethylene, respectively, to prepare oxygen absorbent packages. The oxygen absorbent packages were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, respectively, together with 1,000 ml of air. After sealing, the bag was allowed to stand in an atmosphere of 25°C. After six days the oxygen concentration in the bag was measured to determine the oxygen absorption amount. The results are shown in Table 7. In Examples 17 and 19 water-impregnated absorbent wadding was sealed in the bag together and relative humidity was set at 100%. Example 21 The procedure was repeated in a manner similar to Example 17 except that 2 g of glycerine, 2 g of calcium hydroxide, 0.4 g of ferrous chloride, 1.2 g of silica powders, 0.4 g of activated charcoal and 1.2 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. The amount of oxygen absorbed was 206 ml in this case. Example 22 The procedure was repeated in a manner similar to Example 17 except that 2 g of glycerine, 3.4 g of calcium hydroxide, 0.6 g of manganese chloride, 2.6 g of silica powders and 2 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. The amount of oxygen absorbed was 206 ml in this case. Example 23 The procedure was repeated in a manner similar to Example 17 except that 2 g of glycerine, 3.4 g of calcium hydroxide, 0.6 g of copper sulfate, 2.6 g of silica powders and 3.4 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. The amount of oxygen absorbed was 206 ml in this case. Example 24 After 400 rice weevil imagines were fed in 1 kg of brown rice for a week, the imagines were removed. The remaining brown rice was divided into 40 g each and provided as samples for the following test. After 40 g of brown rice sample and the oxygen absorbent package of Example 30 were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, the bag was sealed to have an air amount in the bag of 1,000 ml. Ten specimens were prepared in a similar manner and stored in a thermostat at 20°C. After storing for 20 days, the bags were unsealed and allowed to stand at 25°C in the thermostat. The number of rice weevils emerged from the brown rice sample was recorded. For control group, the same test was performed as described above except that the oxygen absorbent package was not enclosed in the bag. In this case, the number of rice weevils emerged was made 100%. The results are shown in Table 8. Number of Rice Weevil Emerged Rate of Weevil Emerged Example 24 0 0% Control group 1,500 100% Example 25 After 10 bean jam-filled buns weighing 15 g each and the oxygen absorbent package of Example 23 were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, the bag was sealed to have an air amount in the bag of 1,000 ml and stored at 20°C. After one week the oxygen concentration in the bag and the concentration of carbon dioxide gas were measured and the property of the buns was observed. For control group, the same test was performed as described above except that the oxygen absorbent package was not enclosed in the bag. The results are shown in Table 9. Concentration of Oxygen (%) Concentration of Carbon Dioxide (%) Property of Bea Jam-Filled Bun Example 25 0.01 0 No-abnormality was noted. Control group 16.7 3.8 Mildew generated. Examples 26 through 29 After the respective components for oxygen absorbents shown in Table 10 were mixed with each other, the oxygen absorbents were encased in a small bag (50 mm in length, 80 mm in width) prepared using a packaging material of paper laminated with perforated polyethylene, respectively, to prepare oxygen absorbent packages. The oxygen absorbent packages were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, respectively, together with 1,000 ml of air. After sealing, the bag was allowed to stand in an atmosphere of 25°C. After three days the oxygen concentration in the bag was measured to determine the oxygen absorption amount. The results are shown in Table 10. In Examples 26 and 28 water-impregnated absorbent wadding was sealed in the bag together and relative humidity was set at 100%. Example 30 The procedure was repeated in a manner similar to Example 26 except that 2 g of glycerine, 2 g of calcium hydroxide, 0.4 g of ferrous chloride, 1.2 g of silica powders, 0.4 g of activated charcoal and 1.2 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. The amount of oxygen absorbed was 206 ml in this case. Example 31 The procedure was repeated in a manner similar to Example 26 except that 2 g of glycerine, 2 g of calcium hydroxide, 0.4 g of tannic acid, 0.4 g of ferrous chloride, 1.6 g of silica powders and 1.2 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. The amount of oxygen absorbed was 206 ml in this case. Example 32 The procedure was repeated in a manner similar to Example 26 except that 2 g of glycerine, 3.4 g of calcium hydroxide, 0.4 g of 2,6-di-t-butyl-p-cresol, 0.4 g of copper sulfate, 2.6 g of silica powders and 3.4 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. The amount of oxygen absorbed was 206 ml in this case. Example 33 After 400 rice weevil imagines were fed in 1 kg of brown rice for a week, the imagines were removed. The remaining brown rice was divided into 40 g each and provided as samples for the following test. After 40 g of brown rice sample and the oxygen absorbent package of Example 30 were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, the bag was sealed to have an air amount in the bag of 1,000 ml. Ten specimens were prepared in a similar manner and stored in a thermostat at 20°C. After storing for 20 days, the bags were unsealed and allowed to stand at 25°C in the thermostat. The number of rice weevils emerged from the brown rice sample was recorded. For control group, the same test was performed as described above except that the oxygen absorbent package was not enclosed in the bag. In this case, the number of rice weevils emerged was made 100%. The results are shown in Table 11. Number of Rice Weevil Emerged Rate of Weevil Emerged Example 33 0 0% Control group 1,500 100% Example 34 After 10 bean jam-filled buns weighing 15 g each and the oxygen absorbent package of Example 31 were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, the bag was sealed to have an air amount in the bag of 1,000 ml and stored at 20°C. After one week the oxygen concentration in the bag and the concentration of carbon dioxide gas were measured and the property of the buns was observed. For control group, the same test was performed as described above except that the oxygen absorbent package was not enclosed in the bag. The results are shown in Table 12. Concentration of Oxygen (%) Concentration of Carbon Dioxide (%) Property of Bean Jam-Filled Bun Example 34 0.01 0 No-abnormality was noted. Control group 16.5 4.1 Mildew generated. Examples 35 through 39 After the respective components for oxygen absorbents shown in Table 13 were mixed with each other, the oxygen absorbents were encased in a small bag (50 mm in length, 80 mm in width) prepared using a packaging material of paper laminated with perforated polyethylene, respectively, to prepare oxygen absorbent packages. The oxygen absorbent packages were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, respectively, together with 1,000 ml of air. After sealing, the bag was allowed to stand in an atmosphere of 25°C. After six days the oxygen concentration in the bag was measured to determined the oxygen absorption amount. The results are shown in Table 13. In Examples 35 and 37 water-impregnated absorbent wadding was sealed in the bag together and relative humidity was set at 100%. Example 40 The procedure was repeated in a manner similar to Example 35 except that 2 g of erythritol, 3.3 g of calcium hydroxide, 0.7 g of copper sulfate, 2 g of silica powders, 0.7 g of activated charcoal and 2 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. The amount of oxygen absorbed was 206 ml in this case. Example 41 The procedure was repeated in a manner similar to Example 35 except that 2 g of xylitol, 3.3 g of calcium hydroxide, 0.7 g of copper sulfate, 2 g of silica powders, 0.7 g of activated charcoal and 2 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. The amount of oxygen absorbed was 206 ml in this case. Example 42 The procedure was repeated in a manner similar to Example 35 except that 2 g of sorbitol 3.3 g of calcium hydroxide, 0.7 g of copper sulfate, 2 g of silica powders, 0.7 g of activated charcoal and 2 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. The amount of oxygen absorbed was 206 ml in this case. Example 43 The procedure was repeated in a manner similar to Example 35 except that 2 g of sorbitol, 3.3 g of potassium hydroxide, 0.7 g of copper sulfate, 4.7 g of activated charcoal and 3.3 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. The amount of oxygen absorbed was 206 ml in this case. Example 44 After 400 rice weevil imagines were fed in 1 kg of brown rice for a week, the imagines were removed. The remaining brown rice was divided into 40 g each and provided as samples for the following test. After 40 g of brown rice sample and the oxygen absorbent package of Example 42 were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, the bag was sealed to have an air amount in the bag of 1,000 ml. Ten specimens were prepared in a similar manner and stored in a thermostat at 20°C. After storing for 20 days, the bags were unsealed and allowed to stand at 25°C in the thermostat. The number of rice weevils emerged from the brown rice sample was recorded. For control group, the same test was performed as described above except that the oxygen absorbent package was not enclosed in the bag. In this case, the number of rice weevils emerged was made 100%. The results are shown in Table 14. Number of Rice Weevil Emerged Rate of Weevil Emerged Example 44 0 0% Control group 1,500 100% Example 45 After 10 bean jam-filled buns weighing 15 g each and the oxygen absorbent package of Example 43 were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, the bag was sealed to have an air amount in the bag of 1,000 ml and stored at 20°C. After one week the oxygen concentration in the bag and the concentration of carbon dioxide gas were measured and the property of the buns was observed. For control group, the same test was performed as described above except that the oxygen absorbent package was not enclosed in the bag. The results are shown in Table 15. Concentration of Oxygen (%) Concentration of Carbon Dioxide (%) Property of Bean Jam-Filled Bun Example 45 0.01 0 No-abnormality was noted. Control group 16.7 3.8 Mildew generated. Examples 46 through 49 After the respective components for oxygen absorbents shown in Table 16 were mixed with each other, the oxygen absorbents were encased in a small bag (50 mm in length, 80 mm in width) prepared using a packaging material of paper laminated with perforated polyethylene, respectively, to prepare oxygen absorbent packages. The oxygen absorbent packages were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, respectively, together with 1,000 ml of air. After sealing, the bag was allowed to stand in an atmosphere of 25°C. After three days the oxygen concentration in the bag was measured to determine the oxygen absorption amount. The results are shown in Table 16. In Examples 46 and 48 water-impregnated absorbent wadding was sealed in the bag together and relative humidity was set at 100%. Example 50 The procedure was repeated in a manner similar to Example 46 except that 2 g of erythritol, 3.3 g of calcium hydroxide, 0.7 g of 2,6-di-t-butyl-p-cresol, 0.7 g of copper sulfate, 2 g of silica powders, 0.7 g of activated charcoal and 2 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. The amount of oxygen absorbed was 206 ml in this case. Example 51 The procedure was repeated in a manner similar to Example 46 except that 2 g of xylitol, 3.3 g of calcium hydroxide, 0.7 g of catechol, 0.7 g of copper sulfate, 2 g of silica powders, 0.7 g of activated charcoal and 2 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. The amount of oxygen absorbed was 206 ml in this case. Example 52 The procedure was repeated in a manner similar to Example 46 except that 2 g of sorbitol, 3.3 g of calcium hydroxide, 0.7 g of tannic acid (tannic acid CL, manufactured by Fuji Chemical Industry Co., Ltd.), 0.7 g of copper sulfate, 2 g of silica powders, 0.7 g of activated charcoal and 2 g of water were mixed and the mixture was used as an oxygen absorbent. The oxygen concentration in a bag measured after 2 days showed 0.1% or less. The amount of oxygen absorbed was 206 ml in this case. Example 53 After 400 rice weevil imagines were fed in 1 kg of brown rice for a week, the imagines were removed. The remaining brown rice was divided into 40 g each and provided as samples for the following test. After 40 g of brown rice sample and the oxygen absorbent package of Example 51 were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, the bag was sealed to have an air amount in the bag of 1,000 ml. Ten specimens were prepared in a similar manner and stored in a thermostat at 20°C. After storing for 20 days, the bags were unsealed and allowed to stand at 25°C in the thermostat. The number of rice weevils emerged from the brown rice sample was recorded. For control group, the same test was performed as described above except that the oxygen absorbent package was not enclosed in the bag. In this case, the number of rice weevils emerged was made 100%. The results are shown in Table 17. Number of Rice Weevil Emerged Rate of Weevil Emerged Example 53 0 0% Control group 1,500 100% Example 54 After 10 bean jam-filled buns weighing 15 g each and the oxygen absorbent package of Example 52 were put in a bag laminated with polyvinylidene chloride-coated stretched nylon and polyethylene, the bag was sealed to have an air amount in the bag of 1,000 ml and stored at 20°C. After one week the oxygen concentration in the bag and the concentration of carbon dioxide gas were measured and the property of the buns was observed. For control group, the same test was performed as described above except that the oxygen absorbent package was not enclosed in the bag. The results are shown in Table 18. Concentration of Oxygen (%) Concentration of Carbon Dioxide (%) Property of Bean Jam-Filled Bun Example 54 0.01 0 No-abnormality was noted. Control group 16.5 3.7 Mildew generated. The oxygen absorbent of the present invention is free of iron powders. Therefore, even if the oxygen absorbent is applied to a metal detector after the oxygen absorbent is sealed together with food, the oxygen absorbent is not detected with the metal detector so that inspection is enabled as to whether food is contaminated with foreign matters. In addition, the oxygen absorbent is mainly composed of the 1,2-glycol, glycerine or sugar alcohol and is thus highly safe in view of the components. Furthermore, no noxious gas generates during the reaction. The oxygen absorbent of the present invention is also applicable to substances to be preserved over a wide range which are adversely affected by the presence of oxygen, for example, for preservation, antimolding, prevention from contamination with microorganisms such as, e.g., bacteria, mothproofing, antioxidation, antifading and rust prevention of, e.g., drugs, clothes, furs, medical apparatuses and equipments, precision apparatuses, equipments and parts, electron apparatus and equipments, electron materials and parts and antiques.

Claims: An oxygen absorbent comprising an alkaline substance, a transition metal compound and either at least one 1,2-glycol, or at least one sugar alcohol, or glycerine. The oxygen absorbent of claim 1, wherein the 1,2-glycol is ethylene glycol or propylene glycol. The oxygen absorbent of claim 1 or 2, wherein the alkaline substance is a hydroxide, carbonate, hydrogencarbonate, tertiary phosphate or secondary phosphate of an alkali metal or alkaline earth metal. The oxygen absorbent of claim 3, wherein the alkaline substance is calcium hydroxide. The oxygen absorbent of any of claims 1 to 4, wherein the transition metal compound is an iron, a copper, a manganese or a zink salt. The oxygen absorbent of any of claims 1 to 5, which further comprises a phenolic compound or quinone compound. The oxygen absorbent of claim 6, wherein the phenolic compound is a monovalent phenolic compound. The oxygen absorbent of claim 6, wherein the phenolic compound is a polyvalent phenolic compound. The oxygen absorbent of claim 8, wherein the polyvalent phenolic compound is catechol or gallic acid. The oxygen absorbent of claim 6, wherein the quinone compound is benzoquinone or diphenoquinone. The oxygen absorbent of any of claims 1 to 10, which further comprises water. The oxygen absorbent of any of claims 1 to 11, which further comprises a solid which is sparingly soluble in water. The oxygen absorbent of any of claims 1 to 12, which contains 10 parts or more by weight of the alkaline substance, based on 100 parts by weight of the at least one 1,2-glycol, or at least one sugar alcohol, or glycerine. The oxygen absorbent of any of claims 1 to 13, which contains 1 part or more by weight of the transition metal compound, based on 100 parts by weight of the at least one 1,2-glycol, or at least one sugar alcohol, or glycerine. The oxygen absorbent of any of claims 6 to 10, which contains 1 part or more by weight of the phenolic compound or quinone compound, based on 100 parts by weight of the at least one 1,2-glycol, or at least one sugar alcohol, or glycerine. The oxygen absorbent of claim 11, which contains less than 70 wt% of water, based on the total weight of the absorbent composition. The oxygen absorbent of claim 12, which contains 0,1 to 10000 parts by weight of the compound sparingly soluble in water, based on 100 parts by weight of the at least one 1,2-glycol, or at least one sugar alcohol, or glycerine.

Inventors: HATAKEYAMA HIDETOSHI, KASHIBA TAKASHI, KOMATSU TOSHIO, SUGIHARA YASUO, TAKEUCHI TERUO, HATAKEYAMA, HIDETOSHI, KASHIBA, TAKASHI, KOMATSU, TOSHIO, SUGIHARA, YASUO, TAKEUCHI, TERUO
Applicants: MITSUBISHI GAS CHEMICAL CO, MITSUBISHI GAS CHEMICAL COMPANY, INC.
Application year: 1990
Main classification: A23L3
IPC codes: A23L3