Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-04-20
2001-06-19
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S417000, C524S424000, C524S436000, C523S135000, C423S420200, C423S421000, C423S179500, C047S002000, C047S029500
Reexamination Certificate
active
06248817
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an infrared absorber consisting of a complex hydroxide salt which may be represented by the formula
[Al
2
(Li
(1−x)
.M
2+
(x+y)
(OH)
(6+2y)
]
n
(A
n−
)
(1+x)
.mH
2
O
(wherein M
2+
is a divalent metal, A
n−
is an anion having a valence of n, and m, x and y are numbers respectively in the ranges of 0≦m<5, 0.01 ≦x≦0.5 and 0≦y≦0.5) and an agricultural film prepared by incorporating said infrared absorber into a resin and shaping the mixture into a film.
PRIOR ART
An agricultural film which is being used in a greenhouse cultivation such as growing in houses or tunnels is required to have characteristic properties such that infrared rays radiated from the ground and plants are prevented from being liberated outside the houses or tunnels by the absorption, reflection, etc. during the night while the sunlight is transmitted efficently at a high transmission rate into the houses or tunnels during the daytime. It is known that the infrared rays radiated at a high radiation rate from the ground and plants lie in wavelengths ranging from 5~25 &mgr;m. It is required for the agricultural film to be capable of absorbing infrared rays having wavelengths from 5 to 25 &mgr;m, especially wavelengths in the vicinity of 10 &mgr;m which is the maximum radiation rate.
For the above agricultural film, magnesium carbonate, magnesium silicate, silicon dioxide, aluminum oxide, barium sulfate, calcium sulfate, magnesium hydroxide, aluminum hyroxide, calcium hydroxide, phosphates, silicates, hydrotalcites have been hitherto employed as infrared absorbers.
However, these inorganic powders used hitherto have both respective merits and demerits, and none of them fully meets the above requirements for properties. For example, silicon dioxide and magnesium silicate are excellent in the infrared absorptivity but have problems in the refractive index and dispersibility with the result that they impair the light transmittance of film. Thus, they are not suitable for use as the agricultural film. Also, hydrotalcites are relatively excellent in the dispersibility and refractive index but they are not fully satisfactory in infrared absorptivity.
Also, the Japanese Patent Kokai No. Hei 7-300313 discloses a technics using a lithium aluminum complex hydroxide salt as a heat insulation agent for an agricultural film. This hydroxide salt has a defect that it causes a bad transparency because it has a refractive index of 1.55 which is far apart from the value of about 1.50 that is the refractive index of polyolefin resin.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide an infrared absorber and an agricultural film, said infrared absorber having a high ability to absorb infrared rays and a good dispersibility when incorporated into a resin, and a refractive index which is near to that of the resin so that the film shaped therefrom has excellent heat insulation property and transparency.
As a result of having ardently studied to solve the above problems, the present inventors have found that the above problems may be solved by a basic complex hydroxide salt which may be represented by the following formula (I)
[Al
2
(Li
(1−x)
.M
2+
(x+y)
(OH)
(6+2y)
]
n
(A
n−
)
(1+x)
.mH
2
O (I)
(wherein M
2+
is a divalent metal, A
n−
is an anion having a valence of n, and m, x and y are numbers respectively in the ranges of 0≦m<5, 0.01 ≦x≦0.5 and 0≦y≦0.5) and which has a high ability to absorb infrared rays in the vicinity of 10 &mgr;m of wavelength and which has a basal skeleton composed of an aluminum hydroxide octahedron layer of the gibbsite structure, and have completed the present invention.
That is, the present invention is an infrared absorber which is characterized by containing as an effective ingredient the complex hydroxide salt represented by the above formula (I) [hereinafter, referred to as the compound (I)]. The compound (I) of the present invention is one (in the case of y=0) which has a basic structure composed of a basal skeleton formed by entering lithium and divalent ions into a vacant site of an aluminum hydroxide octahedron layer of the gibbsite structure and an interlayer wherein an anion is introduced.
Also, it is a complex hydroxide salt wherein a hydroxide of divalent metal is entered into the basic structure (in the case of 0<y<1). Although this divalent metal is not limited particularly, Mg, Zn, Ca and the like are preferred from the viewpoints that they may be easily introduced, have white color and meet transparency when incorporated into film.
A
n−
represents a n-varent anion. Examples of anion include c rbonic acid, phosphoric, acid, silicic, acid, acetic acid, propionic acid, adipic acid, benzoic acid, phthalic acid, terephtharic acid, maleic acid, fumaric acid, citric acid, tartaric acid, succinic acid, p-hydrpxybenzoic acid, salicylic acid, picric acid, sulfuric acid, nitric acid, hydrochloric acid, iodine, fluorine, bromine and the like. Phosphoric acid, carbonic acid and silicic acid may be preferably used.
In the case that the infrared absorber of the present invention, that is the infrared absorber which is characterized by containing as an effective ingredient the compound (I) as above-mentioned is used to be incorporated into films such as agricultural film and so on, one having a very fine particle, a high dispersibility and a relatively developed crystal are preferred. Therefore, the average secondary particle size is preferably below 3 &mgr;m, more preferably below 1 &mgr;m. Also, the BET specific surface area is preferably below 50 m
2
/g, more preferably below 20 m
2
/g.
The followings illustrate in detailes a process for preparing the compound (I) of the present invention where M
2+
is Mg as a specific example.
The compound (I) of the present invention in the case of M
2+
being Mg and y=0, a basic aluminum magnesium complex hydroxide of carbonate ion type [Al
2
Li
(1−x)
.Mg
(x)
(OH)
6
]
n
(CO
3
)
(1+x)
.mH
2
O may be prepared by the following process.
Aluminum hydroxide is reacted with lithium carbonate and carbonate of magnesium such as magnesium carbonate and basic magnesium carbonate in an aqueous medium under heat treatment.
Lithium carbonate and magnesium carbonate or basic magnesium carbonate may be used in such a amount that [Li/Al
2
O
3
(molar ratio)]+[MgO/Al
2
O
3
(molar ratio)] becomes 1 with respect to the content of Al
2
O
3
in aluminum hydroxide. However, slight excess of lithium component may be added.
A complex hydroxide salt (in the case of 0<y≦0.5) wherein magnesium hydroxide is introduced may be prepared by reacting aluminum hydroxide with lithium carbonate, carbonate of magnesium such as magnesium carbonate and basic magnesium carbonate and one or more of water soluble magnesium salts selected from the group consisting of magnesium chloride, magnesium sulfate, magnesium nitrate and magnesium hydroxide in an aqueous medium under heat treatment. In this case too, lithium carbonate and magnesium carbonate or basic magnesium carbonate may be used in such a amount that [Li/Al
2
O
3
(molar ratio)]+[MgO/Al
2
O
3
(molar ratio)] becomes 1 with respect to the content of Al
2
O
3
in aluminum hydroxide. However, slight excess of lithium component may be added.
The temperature range for heat treatment is preferably an appropriate temperature ranging from an ordinary temperature to 200° C., more preferably 90~160° C., most preferably 110~160° C. In the case where treatment temperature is lower than the ordinary temperature, it is not preferable because the extent of crystallinity becomes low.
The above complex metal hydroxide salt of carbonate ion type may be treated with acids, for example mineral acids such as nitric acid, halogenic acid such as hydrochloric acid, sulfuric acid and so on or organic acids, for example mono
Fuji Chemical Industry Co., Ltd.
Harlan R.
Nath & Associates PLLC
Novick Harold L.
Wu David W.
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