Patent Grant
8062540
This application is the U.S. National Phase under 35 U.S.C. §371 of International Application PCT/JP2008/004033, filed Dec. 26, 2008, which claims priority to Japanese Patent Application No. 2007-340943, filed Dec. 28, 2007. The International Application was published under PCT Article 21(2) in a language other than English.
The present invention relates to a natural leather associated with low volatilization volumes of VOCs (volatile organic compounds) (hereinafter also referred to as “low-VOC leather”; the terms “leather”, “leather skin”, and “natural leather” are hereinafter used synonymously).
Seats, steering wheels, shift knobs, instrument panels and other automobile interior parts use natural leathers.
The process of manufacturing a natural leather from a natural hide comprises a pre-treatment step before tanning, a tanning step where a tanning agent is used, a re-tanning step where again a tanning agent is used, a dyeing step where a dye is used, a greasing step where a greasing agent is used, a drying step, and a coating film-forming step. When implementing this series of steps, it is possible to complete the tanning step and successively perform the re-tanning and subsequent steps, or move to a different location to perform the re-tanning and subsequent steps there.
In the tanning step, chromium compounds have been used as tanning agents. However, the current trend is to switch to methods where tanning agents constituted by glutaraldehyde and other materials other than chromium compounds are used.
In the re-tanning step, re-tanning is performed using chromium compounds, or using other types of re-tanning agents such as vegetable tanning agents, synthetic tanning agents and glutaraldehyde.
As for dyes, various dyes are used including acid dyes having a sulfonic acid group or carboxylic acid group, direct dyes having the sulfonic acid group, basic dyes having a nitrogen base, reactive dyes, and sulfur dyes.
As for greasing agents, anionic greasing agents, cationic greasing agents, amphoteric greasing agents, nonionic greasing agents and fatty acid soaps are used, among others.
After the greasing step and subsequent drying step, a coating material is applied onto the leather to form a coating film. Polyurethane resin and other synthetic resins are used in the forming of coating film.
Natural leathers manufactured by the aforementioned process are used as covering materials for automobile interior parts, etc. Natural leathers having unique characteristics such as wear resistance and favorable touch can be obtained. Needless to say, automobile interior parts using leathers have been developed under strict control conditions. When the cabin environment of automobiles fitted with such automobile interior parts was measured, however, formaldehyde, acetaldehyde and other VOCs (volatile organic compounds) were detected, indicating that these compounds were present in air in the cabin of these automobiles.
The Japan Automobile Manufacturers Association is working to make sure VOC concentrations in automobile cabins meet the guideline values set by the Ministry of Health, Labour and Welfare, and accordingly automakers and natural leather manufacturers are doing their best to bring VOC concentrations in automobile cabins to compliance with the guideline values.
Reasons why the aforementioned VOCs generate or specific mechanisms of their generation are not yet understood fully and no specific methods are available, either, to minimize the amounts of formaldehyde, acetaldehyde, etc., in automobile cabins to the target values or below, and accordingly the market is awaiting effective solutions to be developed as soon as possible.
Natural leathers used in automobile cabins, manufactured from animal hides, are known to be exposed to extremely high temperatures, much higher than the temperatures in normal living spaces, when the automobile is left under the direct sun with all its windows closed. When this occurs, volatile components in materials volatilize at these high temperatures, attach to the glass surface where they are cooled and condense again, and these deposits of re-condensates cause the window glass to fog. The fogged glass obstructs the driver's view and reduces driving safety. This phenomenon is called “fogging.” Fogging occurs due to volatilization of volatile components at high temperatures (100 to 120° C.), and is different from the problem dealt with by the present invention which is caused by formaldehyde, acetaldehyde, etc., generated in the cabin environment even when not heated.
Methods to reduce the generation of formaldehyde, acetaldehyde, etc., in automobile cabins include those listed below. Because tanning agents used in the tanning step are cited as a cause of formaldehyde generation, tanning agents that do not generate formaldehyde, such as those using hydroxyalkylphosphine compounds, are being developed (Patent Literature 1, Published Japanese Translation of PCT International Patent Application No. Hei 6-502886; Patent Literature 2, Japanese Patent Laid-open No. 2005-272725; and Patent Literature 3, Japanese Patent Laid-open No. 2006-8723).
Currently, obtaining synthetic tanning agents from phenolsulfonic acid and formaldehyde is considered the most appropriate approach (Patent Literature 4, Japanese Patent Laid-open No. 2000-119700). However, tanning and re-tanning using these newly developed tanning agents mentioned above is not considered as effective as the results achieved by conventional tanning and re-tanning treatments, and therefore this approach does not provide a sufficient solution. Also, this approach does not touch on prevention of another problem currently debated, or specifically volatilization of residual acetaldehyde from natural leathers, and therefore this approach is not expected to offer a fundamental solution at the present.
A method is known that comprises the first step where the target leather is tanned without using formalin, and the second step where the aforementioned leather completing the aforementioned first step is tanned with oil in a rotary drum and the temperature in the aforementioned rotary drum is gradually raised to oxidize the leather in the aforementioned rotary drum (Patent Literature 5, Japanese Patent Laid-open No. 2005-272725). Here, formalin-free tanning is performed using glutaraldehyde, and since the methods presenting problems today do not use glutaraldehyde, the aforementioned method cannot be used to deal with formaldehyde and acetaldehyde presenting problems today.
Currently no effective methods are available that offer an immediate solution to the challenge of reducing/preventing generation of formaldehyde or acetaldehyde from within natural leathers that are manufactured by a series of steps including tanning operation, and the market is awaiting effective solutions to be developed as soon as possible.
Methods to remove formaldehyde and acetaldehyde, which are used in areas other than manufacturing of natural leathers, include the following:
The object of the present invention is to provide, in relating to a natural leather obtained by tanning, re-tanning, dyeing and greasing steps, or natural leather obtained by forming a coating film on it after the aforementioned processes: a natural leather that inhibits or prevents separation and release from the natural leather of formaldehyde and acetaldehyde that break free as a result of breakdown of the internal structure of the natural leather or any substance taken into the structure; as well as a natural leather treatment agent capable of inhibiting or preventing release from the leather of formaldehyde and acetaldehyde that break free from a tanning agent, greasing agent or other chemical agent added and taken into the leather in the greasing step, etc., of the natural leather manufacturing process designed for manufacturing such natural leather.
The inventors of the present invention tackled the aforementioned object and found the need to examine the following points:
According to the present invention, which relates to a natural leather completing the greasing step and drying step after tanning, re-tanning and dyeing, or natural leather obtained by forming a coating film on it after the drying step, a natural leather can be obtained that inhibits or prevents formaldehyde and acetaldehyde from breaking free inside and coming out of the natural leather as a result of breakdown of the internal structure of the natural leather or any treatment agent taken into the natural leather. A natural leather treatment agent can be obtained which is added in the greasing step of the natural leather manufacturing process for manufacturing such natural leather, wherein the natural leather treatment agent greases the natural leather and at the same time inhibits or prevents formaldehyde and acetaldehyde from breaking free inside and coming out of the natural leather so that formaldehyde and acetaldehyde generated in the natural leather can be confined in the natural leather.
In relation to a natural leather treated with a treatment agent in the greasing step following the series of steps in the manufacturing process for natural leather including pre-treatment for tanning, tanning, re-tanning and dyeing, and also in relation to a natural leather obtained by forming a coating film on it after the subsequent drying step, formaldehyde and acetaldehyde are observed to break free and come out of the natural leather as a result of breakdown of the internal structure of the natural leather or any treatment agent taken into the natural leather. Generation of formaldehyde and acetaldehyde is not desirable as it presents health risks to users of natural leathers.
The present invention provides a natural leather obtained by being treated in a series of steps including pre-treatment for tanning the natural leather, tanning, re-tanning and dyeing, using treatment agents including tanning agent, re-tanning agent and dye, and then treated in the subsequent greasing step using a natural leather treatment agent containing a greasing agent as well as a trapping agent or fixing agent for confining in the natural leather the formaldehyde and acetaldehyde generated in the natural leather.
The trapping agent or fixing agent for confining in the natural leather the formaldehyde and acetaldehyde generated in the natural leather acts to inhibit or prevent formaldehyde and acetaldehyde from breaking free and coming out of the natural leather as a result of breakdown of any substance taken into the natural leather, thereby confining in the natural leather the formaldehyde and acetaldehyde generating in the natural leather.
Also, the present invention provides a natural leather treatment agent containing a greasing agent for use in the greasing step for obtaining natural leather, as well as a trapping agent or fixing agent for confining in the natural leather the formaldehyde and acetaldehyde generating in the natural leather.
The present invention relates to a series of treatment steps for natural leather implemented by using treatment agents, and is characterized by the greasing step which is the final stage of these treatment steps.
The series of treatment steps for manufacturing natural leather are explained below, and the aforementioned unique characteristics are explained in detail in the explanation of the greasing step.
The series of treatment steps for manufacturing natural leather are explained.
The series of treatment steps for manufacturing natural leather are divided into a process comprising mainly pre-treatment for tanning and tanning steps (
The pre-treatment for tanning and tanning steps are included in the process from water washing and soaking of material hide to trimming (
In the water washing/soaking step for material hide, the material hide that has been stored at low temperature to maintain freshness and prevent decay is transferred into the lime drum, where water is added to the salt-cured material hide to bring it back to the state of raw hide, and then salt and impurities are removed and pH is adjusted for liming.
In the fleshing/trimming step, the material hide is transferred onto the fleshing machine and trimming machine, where excess fat and other gluey substances are mechanically removed, along with salt and impurities, and then the edges are trimmed. In the liming step, the material hide is transferred into the lime drum, where hairs on the surface of hide are dissolved and scudding is implemented, after which lime is permeated into the hide to loosen the fibers.
In the raw band splitting step, the material hide is transferred onto the band machine, where the hide is strained to a thickness appropriate for the specific purpose and also split into the surface layer and base.
The deliming, enzymatic hydrolysis and pickling steps are as follows.
Limes from the aforementioned liming step are removed, enzymatic hydrolysis is implemented using an enzyme, and the material hide is pickled.
In the tanning step, a tanning agent is supplied as a treatment agent and the obtained hide is tanned with the tanning agent to manufacture a leather.
In the squeezing step, the leather is transferred into the water draining machine to squeeze the leather. Next, squeezed leathers are sorted and graded according to their surface conditions such as presence of flaws or holes, area, etc.
In the shaving step, the leather is transferred onto the shaving machine to shave it to a thickness appropriate for the specific purpose. In the trimming step, unnecessary waste parts, etc., are cut on the trimming table to prevent breakage and thereby increase work efficiency in the subsequent steps.
The aforementioned tanning step is where the hide is treated in the presence of a tanning agent and water under an acid condition. The tanning agent induces cross-linking in the collagen substance in the hide and gives resistance to heat, microorganisms and chemical substances, as well as flexibility, to the hide.
For the tanning agent, a trivalent chromium complex such as a chromium compound using a hexaaqua crystal sulfate expressed by Cr2(SO4)3 or an aldehyde compound including glutaraldehyde is used. These substances are traditionally known as tanning agents and any appropriate product available on the market can be purchased and used.
Examples of chromium complex products include the following:
ChromitanB, ChromitanMS, ChromitanFM, BaychromaCH, BaychromaCL, BlancorolRN, BlancorolRC, etc.
In the tanning step, chromium salt containing 2 to 2.5% of Cr2O3 relative to the untreated hide is introduced, but reportedly only 70 to 80% of it is fixed in the hide and 20 to 30% is released into the spillage.
In addition to chromium, glutaraldehyde can also be used as a tanning agent. This glutaraldehyde is explained below. Glutaraldehyde is a known substance and if a glutaraldehyde product available on the market is to be used, Relugan GT-50, Relugan GTW, Ucar Tanning Agent GA-25, Ucar Tanning Agent GA-50, etc., can be used.
The use quantity of glutaraldehyde is approx. 1 to 10 percent by weight relative to the weight of leather (Japanese Patent Laid-open No. Hei 08-232000).
All of these tanning agents chemically bind with the components of natural leather.
In addition to the above, synthetic tanning agents (synthetic tanning agents are explained in connection with the re-tanning step) and vegetable tannins (MimosaME, MimosaFE, Quebracho, etc.) can be used. These substances are traditionally known as tanning agents and any appropriate product available on the market can be purchased and used.
The re-tanning step, dyeing step and greasing step are performed in the same drum (
When each step ends, thorough water wash is performed to prevent the result of the preceding step from affecting the next step.
In the re-tanning step, a synthetic tanning agent, vegetable tanning agent, etc., is used as a re-tanning agent. In some cases, the aforementioned tanning agents such as chromium, glutaraldehyde, etc., may be added.
Neutralization is confirmed before re-tanning. To be specific, a pH indicator is dripped onto a cross-section of the natural leather and how the color change is observed. As a rough guide, the surface layer should have a pH value of around 5 or 6, and inner layer 3 to 4, for the upper leather type.
Preferably a synthetic tanning agent or other tanning agent used in the re-tanning step should be an aqueous solution containing 50 to 200 percent by weight relative to the weight of the leather used.
The treatment condition for such tanning agent should be pH 3.0 to 8.0, or more preferably 3.5 to 6.5. The re-tanning time should be preferably 1.5 to 24 hours, or more preferably 2 to 8 hours.
In the dyeing step, the leather is dyed using a dye.
In the dyeing step, a dye corresponding to the desired color is used.
Although dyes should not generate formaldehyde and acetaldehyde at normal room temperatures, the following explanation is given regarding dyes.
The leather obtained through the aforementioned treatment method is dyed using an anionic water-based dye. Here, this anionic water-based dye is constituted by a water-based medium, dye, etc. A water-based medium may be water or mixture of water and alcohol or other water-soluble medium. Also note that although any dye can be used that can be used to add color to the leather, representative examples include acid dyes and reactive dyes.
Acid dyes include C. I. Acid Black 1, C. I. Acid Black 26, C. I. Acid Black 52, C. I. Acid Green 9, C. I. Acid Green 25, C. I. Acid Brown 2, C. I. Acid Brown 13, C. I. Acid Violet 43, C. I. Acid Violet 49, C. I. Acid Orange 7, C. I. Acid Orange 56, C. I. Acid Orange 67, C. I. Acid Blue 40, C. I. Acid Blue 45, C. I. Acid Blue 74, C. I. Acid Blue 92, C. I. Acid Blue 113, C. I. Acid Blue 127, C. I. Acid Blue 185, C. I. Acid Red 18, C. I. Acid Red 27, C. I. Acid Red 52, C. I. Acid Red 82, C. I. Acid Red 87, C. I. Acid Red 114, C. I. Acid Red 186, C. I. Acid Red 266, C. I. Acid Yellow 1, C. I. Acid Yellow 7, C. I. Acid Yellow 23, C. I. Acid Yellow 110, etc.
Reactive dyes include C. I. Acid Black 5, C. I. Acid Brown 1, C. I. Acid Violet 2, C. I. Acid Orange 1, C. I. Acid Orange 2, C. I. Acid Blue 4, C. I. Acid Blue 19, C. I. Acid Red 6, C. I. Acid Red 17, C. I. Acid Yellow 3, C. I. Acid Yellow 17, etc. The aforementioned dyes can be combined. Also, a dye or dyes is/are dissolved and/or dispersed in a water-based medium before application to adjust to a desired color. It is also possible to add pigments or other coloring materials to the extent that it does not inhibit the coloring effect.
As for the dyeing method, the following explains dying the surface of an upper leather made of chromium-tanned cowhide of approx. 1.4 mm in thickness.
After the re-tanning, the shaved leather (completing the shaving step and trimming step) is washed with 400% of water based on the wet weight of the shaved leather being 100% (the wet weight of the shaving leather is hereinafter used as the reference), and the leather is dyed in an aqueous solution constituted by 250% of water (50° C.), 0.5% of level dyeing agent and 2.5% of surface dye (1:20). One half of the step is implemented by 20 minutes of rotation, and the remaining half by 30 minutes of rotation. The fixing operation using 1% of formic acid (1:10) comprises the two-thirds of the step implemented by 10 minutes of rotation, and the remaining one-third by 10 minutes of operation.
The greasing step is performed after the dyeing step following re-tanning, and designed to add the required flexibility to the leather product by treating the leather with an oil agent called “greasing agent.” Not a few greasing agents have surface activation property. As a result, these agents permeate into the natural leather easily.
The dyed leather introduced to the greasing step is wet with water, and flexibility of fibers is retained by the water present between the fibers constituting fiber bundles. If this water dries up, fibers will stick together and both the fibers and structure will harden. Accordingly, it is effective to apply an oil agent to the space between fibers, before the water dries, to inhibit sticking of fibers. Also, functions to protect leather fibers (water repellency, water-proofness), touch and bulge are added. This is the purpose of the greasing step, where a greasing agent is used.
As for the conditions of the greasing step, the dyed leather is treated in the same drum at a temperature condition of 50 to 60° C. using a natural leather treatment agent containing a greasing agent as well as a treatment agent for confining in the natural leather the formaldehyde and acetaldehyde generating in the natural leather.
The natural leather treatment agent conforming to the present invention, which is introduced in the greasing step, is a composition constituted by the components specified below.
Based on the wet weight of shaved leather being 100%, 1 to 8 percent by weight of greasing agent, 0.5 to 3 percent by weight (when hydrazide compound is contained) or 0.6 to 6.0 percent by weight (when both sodium hydrogen sulfite and hydrazide compound are contained) of treatment agent that confines in the natural leather the formaldehyde and acetaldehyde generating in the natural leather, and 50 to 200 percent of water are contained.
The greasing agent has the effect of permeating into the leather and thereby preventing the fibers constituting the leather from sticking together when the water dries, while also adding flexibility to the leather by improving the sliding of fibers against each other after drying. The greasing agent is a composition constituted by such components and water.
The treatment agent that confines in the natural leather the formaldehyde and acetaldehyde generating in the natural leather is taken into the natural leather together with the greasing agent and inhibits or prevents formaldehyde and acetaldehyde from breaking free and coming out of the natural leather as a result of breakdown of any substance taken into the natural leather, thereby effectively confining in the natural leather and preventing the leakage therefrom of the formaldehyde and acetaldehyde generating in the natural leather. Water dissolves the greasing agent and treatment agent that confines in the natural leather the formaldehyde and acetaldehyde generating in the natural leather, and becomes a medium that can easily permeate into the natural leather.
The specific substance used is a hydrazide compound, or a sodium hydrogen sulfite and hydrazide compound. If a hydrazide compound is used, its content must not exceed 3 percent by weight because then precipitation will occur and greasing will be negatively affected. Normally a hydrazide compound content of approx. 2 percent by weight results in small contents of formaldehyde and acetaldehyde.
Under the present invention, a natural leather is treated by introducing into the drum used in the greasing step a natural leather treatment agent containing a greasing agent for natural leather as well as a treatment agent for confining in the natural leather the formaldehyde and acetaldehyde generating in the natural leather.
This natural leather treatment agent is explained below.
The greasing agent and the treatment agent that confines in the natural leather the formaldehyde and acetaldehyde generating in the natural leather may be pre-mixed and introduced into the drum in the greasing step, or the greasing agent may be introduced separately from the treatment agent that confines in the natural leather the formaldehyde and acetaldehyde generating in the natural leather.
Greasing agents include the following, and any one of these may be selected and used.
The aforementioned greasing agents are combined with the surface active agents specified below.
The calculations of greasing agents actually used are explained below.
The (measured) amount of greasing agent considered to be actually remaining in the natural leather is the amount of greasing agent used, less the (measured) amount of greasing agent contained in the residual liquid left in the greasing step and (measured) amount of greasing agent washed away when the natural leather is washed with water.
The amount of greasing agent initially used was 1 to 8 (parts by weight; same applies hereinafter unless otherwise specified) based on the dry weight of shaved leather being 100 parts. The amount of greasing agent contained in the residual liquid remaining in the greasing step was 0.2 to 1.6, and the amount of greasing agent washed away when the natural leather was washed with water was 0.1 to 0.8. Accordingly, the amount of greasing agent considered to be actually remaining in the natural leather is 0.7 to 5.6.
Also note that the (measured) amount of treatment agent considered to be actually remaining in the natural leather, where such treatment agent is one that confines in the natural leather the formaldehyde and acetaldehyde generating in the natural leather, is the (measured) amount of treatment agent actually introduced, less the (measured) amount of treatment agent added in the natural leather greasing step and now contained in the residual liquid remaining in the greasing step and (measured) amount of treatment agent washed away when the natural leather is washed with water.
The (measured) amount of treatment agent initially added and considered to be actually remaining in the natural leather was 0.5 to 3, the (measured) amount of treatment agent contained in the residual liquid was 0.1 to 0.6, and the (measured) amount of treatment agent considered to have been washed away when the natural leather was washed with water was 0.05 to 0.3. Accordingly, the amount of treatment agent considered to be actually remaining in the natural leather is 0.35 to 2.1.
After the greasing step, the natural leather is washed thoroughly with water as deemed appropriate and the cleaned leather is then heated to a range of 60 to 80° C. This way, residual sodium hydrogen sulfite and hydrazide compound can be removed.
The aforementioned hydrazide compound is not specifically limited, and examples include monohydrazide compounds having one hydrazide group in the molecule, dihydrazide compounds having two hydrazide groups in the molecule, and polyhydrazide compounds having three or more hydrazide groups in the molecule, among others.
Specific examples of monohydrazide compounds include those expressed by General Formula (1) below:
[Chemical Formula 1]
R—CO—NHNH2 (1)
(In the formula, R represents a hydrogen atom, alkyl group or aryl group that can have a substitutional group.)
In General Formula (1) above, an alkyl group represented by R may be, for example, a methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, n-undecyl group or other straight-chain alkyl group with 1 to 12 carbons. If it is an aryl group, examples include a phenyl group, biphenyl group and naphthyl group, among others. Of these, use of a phenyl group is preferable. A substitutional group any such aryl group can have may be, for example, a hydroxyl group, fluorine, chlorine, bromine or other halogen atom, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, tert-butyl group, iso-butyl group or other straight- or branched-chain alkyl group with 1 to 4 carbons.
More specifically, a hydrazide compound expressed by General Formula (1) above may be, for example, lauric acid hydrazide, salicylic acid hydrazide, formhydrazide, acetohydrazide, propionic acid hydrazide, p-hydroxy benzoic acid hydrazide, naphthoic acid hydrazide or 3-hydroxy-2-naphthoic acid hydrazide, among others.
Specific examples of dihydrazide compounds include those expressed by General Formula (2) below:
[Chemical Formula 2]
H2NHN—X—NHNH2 (2)
(In the formula, X represents group-CO— or group-CO-A-CO—. A represents an alkylene group or arylene group.)
In General Formula (2) above, an alkylene group represented by A may be, for example, a methylene group, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group, heptamethylene group, octamethylene group, nonamethylene group, decamethylene group, undecamethylene group or other straight-chain alkylene group with 1 to 12 carbons. Examples of an arylene group include, among others, a phenylene group, biphenylene group, naphthylene group, anthrylene group and phenanthrylene group. Of these, use of a phenylene group, naphthylene group, etc., is preferable. A substitutional group any such arylene group can have may be selected from the same examples of substitutional groups cited for the aforementioned aryl group.
To be specific, a dihydrazide compound expressed by General Formula (2) above may be, for example, an oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, diglycolic acid dihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, dimeric acid dihydrazide, 2,6-naphthoic acid dihydrazide and other dibasic acid dihydrazides.
Furthermore, the various dibasic acid dihydrazide compounds described in Examined Japanese Patent Laid-open No. Hei 2-4607, and 2,4-dihydrazide-6-methyl amino-sym-triazine, etc., can also be used as dihydrazides for the aforementioned purpose.
All are known substances and any appropriate commercial product can be purchased and used. Specific products include Chemcatch by Otsuka Chemical.
The greased leather is treated as follows.
The greasing step is followed by water draining (setter), hang drying and conditioning (adjustment of water content). In the vibration step, the leather is transferred onto the vibration machine where its foot, periphery and other hard areas are softened and lines generated from drum milling are removed to increase the surface area. In the drum milling step, the leather is transferred into the rotary drum to loosen the leather fibers that have been dried. In the subsequent drying, buffing and vibration step, the leather is transferred onto the fin-back machine where the milled leather is secured by toggle mechanisms and stretched, dried (on a net), and flattened. The leather is then transferred onto the vibration machine to loosen the fibers, soften the foot, periphery and other hard areas, and remove lines generated from drum milling to increase the surface area. Thereafter, the obtained product undergoes an intermediate inspection to check the grade, grains, texture, color, thickness and other items.
The natural leather obtained by the aforementioned steps has, in the natural leather, the tanning agent, re-tanning agent, dye, greasing agent, and treatment agent that confines in the natural leather the formaldehyde and acetaldehyde generating in the natural leather.
To make this natural leather into a product, a coating film is formed on the surface of natural leather in the manner explained below.
The coating step is where a coating film is formed, using a coating material, on the surface of the natural leather that has been heated after the greasing step.
A base coat layer constituted by a water-based coating agent containing pigment is coated onto the surface of the base of natural leather, a color coat layer constituted by a water-based coating agent is coated onto the aforementioned coat layer, and a top coat layer is formed on the aforementioned coat layer.
(1) Base Coat Layer
The natural leather obtained by the aforementioned steps has, in the natural leather, the tanning agent, re-tanning agent, dye, greasing agent, and treatment agent that confines in the natural leather the formaldehyde and acetaldehyde generating in the natural leather, wherein a coating film constituted by three layers is formed on the surface of such natural leather.
It has been known that, depending on the coating film constituted by three layers provided on the surface of natural leather, such coating film does not inhibit or prevent formaldehyde and acetaldehyde generating in the natural leather. Accordingly, formaldehyde and acetaldehyde generating from the natural leather formed by the aforementioned steps were checked. The results were used to evaluate if the natural leather treated by the series of steps until greasing, according to the present invention, can inhibit or prevent formaldehyde and acetaldehyde from breaking free and separating from/coming out of the natural leather as a result of breakdown of any substance taken into or already present in the natural leather.
The natural leather manufactured through the aforementioned steps was tested by the method explained below to check if generation of formaldehyde and acetaldehyde would be measured.
Formaldehyde and acetaldehyde were analyzed using the Tedlar bag method.
Under the Tedlar bag method, the sample leather is cut to the size of 1 DS (10 cm×10 cm) and put in a Tedlar bag, after which nitrogen is charged and the bag is sealed. The bag is then heated to cause aldehydes to volatilize from the leather. In this condition, a pump is used to suction the gas out of the bag and let aldehydes be adsorbed by a special dinitrophenyl hydrazide (DNPH) cartridge.
The adsorbed substances are then eluted using acetonitrile and the obtained solution is measured by high-speed liquid chromatography.
According to the measurements obtained so far, a natural leather treatment agent containing a greasing agent along with sodium hydrogen sulfite resulted in adsorption of up to 0.709 μg/DS of formaldehyde and up to 2.379 μg/DS of acetaldehyde, while a natural leather treatment agent containing a greasing agent along with sodium hydrogen sulfite and hydrazide compound resulted in adsorption of up to 0.230 μg/DS of formaldehyde and up to 0.232 μg/DS of acetaldehyde.
The natural leather treatment agent for use in the greasing step contains a greasing agent as well as a trapping agent or fixing agent for confining in the natural leather the formaldehyde and acetaldehyde generating in the natural leather.
Natural Leather Treatment Agent for Use in the Greasing Step of Natural Leather
Conditions of Natural Leather Treatment Agent
Treatment temperature: 50 to 60° C.
pH: 5
The greasing agent, and the trapping agent or fixing agent for containing in the natural leather the formaldehyde and acetaldehyde generating in the natural leather, used in amounts relative to 100 parts by wet weight of the chromium-tanned leather (wet blue), are as follows:
Ratio of Natural Leather Treatment Agent Used and Leather (Parts by Weight)
A coating film constituted by a base coat layer, color coat layer and topcoat layer, each made of a two-component aliphatic polyurethane, was formed on the natural leather obtained under the aforementioned conditions, by spray coating over the entire surface.
Analysis Results
The treated leather thus obtained was evaluated by the Tedlar bag method to analyze the generated amounts of formaldehyde and acetaldehyde, the results of which are as follows:
All conditions are the same as those used in Example 1, except for the following
Analysis Results
The treated leather thus obtained was evaluated by the Tedlar bag method to analyze the generated amounts of formaldehyde and acetaldehyde, the results of which are as follows:
All conditions are the same as those used in Example 1, except for the following
Analysis Results
The treated leather thus obtained was evaluated by the Tedlar bag method to analyze the generated amounts of formaldehyde and acetaldehyde, the results of which are as follows:
All conditions are the same as those used in Example 1, except for the following
Analysis Results
The treated leather thus obtained was evaluated by the Tedlar bag method to analyze the generated amounts of formaldehyde and acetaldehyde, the results of which are as follows:
Analysis Results
The treated leather thus obtained was evaluated by the Tedlar bag method to analyze the generated amounts of formaldehyde and acetaldehyde, the results of which are as follows:
The above results are organized in Table 1.
As shown, generation of formaldehyde was inhibited in Comparative Example 1.
In Example 1 where dihydrazide was used, generation of formaldehyde and acetaldehyde was inhibited.
Results of Examples 2 and 3 show that increasing the added amount of dihydrazide would inhibit generation of formaldehyde and acetaldehyde more effectively.
Natural leather was treated in the same manner as in Examples 1 to 3 mentioned above, except that phosphorylated oil was used as a greasing agent, and the same results were obtained.
Natural leather was treated in the same manner as in Examples 1 to 3 mentioned above, except that a nonionic greasing agent was used, and the same results were obtained.
Natural leather was treated in the same manner as in Examples 1 to 3 mentioned above, except that vegetable oil was used as a greasing agent, and the same results were obtained.
Natural leather was treated in the same manner as in Examples 1 to 3 mentioned above, except that sulfited oil was used as a greasing agent, and the same results were obtained.
Natural leather was treated in the same manner as in Examples 1 to 3 mentioned above, except that sulfated oil was used as a greasing agent, and the same results were obtained.
The present invention discusses a natural leather used for car seats and automobile interior parts. The natural leather for preventing generation of formaldehyde and acetaldehyde, as proposed by the present invention, can also be utilized in place of natural leathers applied for general products, to prevent generation of formaldehyde and acetaldehyde.
| Number | Date | Country | Kind |
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| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/004033 | 12/26/2008 | WO | 00 | 6/25/2010 |
| Publishing Document | Publishing Date | Country | Kind |
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| WO2009/084236 | 7/9/2009 | WO | A |
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