Stock material or miscellaneous articles – Composite – Of carbohydrate
Reexamination Certificate
2002-09-23
2004-07-27
Kiliman, Leszek B (Department: 1773)
Stock material or miscellaneous articles
Composite
Of carbohydrate
C428S535000, C428S536000, C428S537100, C428S507000, C428S511000, C428S512000, C428S513000, C428S514000, C427S201000, C427S202000, C427S203000, C427S207100, C427S208000, C524S521000, C524S523000, C524S524000
Reexamination Certificate
active
06767646
ABSTRACT:
The present invention relates to a process for impregnating base paper or fiber webs with an aqueous dispersion of a polymer of free-radically polymerizable compounds (monomers), which comprises from 0.1 to 5% by weight of the monomers being methacrylic acid.
The invention further relates to impregnated base papers or fiber webs obtainable by the process and to the use of the impregnated base papers for producing decorative films.
Chipboard is frequently coated with decorative films and used in that state for manufacturing furniture. Decorative film consists essentially of an impregnated base paper which has been printed with a printing ink and so has the desired appearance and is generally coated with a protective coating of a formaldehyde resin.
The application properties of the decorative film are essentially determined by the impregnated base paper. Impregnating the base paper should in particular increase the strength of the base paper and effect good compatibility with the printing ink and the protective coating and in particular good cohesion between the layers in the decorative film.
EP-A-889 168 and EP-A-223 922 disclose impregnating base paper with polymer dispersions.
Useful binders for this application include commercially available emulsion polymers containing small amounts of acrylic acid and methylolmethacrylamide (e.g. Acronal® S305 D).
Prior art impregnated base papers frequently have unsatisfactory application properties. More particularly, the penetration depth into the base paper of the polymer dispersion used for the impregnation is not sufficient. Insufficient penetration depth and hence insufficient impregnation result in poor application properties, for example poor strengths of the decorative film or easy cleavability of the decorative film into individual layers.
The polymer dispersion used for impregnating should also have very low viscosity and should not coagulate during processing despite high shearing stresses. The polymer dispersion should further be readily compatible with urea- or melamine-formaldehyde resins in order that it may also be used mixed with these resins.
It is an object of the present invention to provide an impregnated base paper or fiber web meeting the above requirements.
We have found that this object is achieved by the process defined at the beginning and by the impregnated base paper or fiber web obtainable thereby.
The process of the invention utilizes an aqueous dispersion of a polymer to impregnate base paper or fiber web.
The polymer is polymerized from free-radically polymerizable compounds (monomers) and obtainable by free-radical polymerization of these monomers.
The weight percentages which follow are each based on the polymer.
The polymer contains from 0.1 to 5% by weight, preferably 0.5 to 3% by weight, particularly preferably from 1 to 2.5% by weight, of methacrylic acid (MAS).
The polymer preferably additionally contains methylolmethacrylamide (MAMol), especially in amounts of from 0.1 to 5% by weight, preferably from 1 to 4% by weight, particularly preferably from 1.0 to 2.5% by weight.
Preferably, as well as MAS and MAMol, the polymer also contains methylolacrylamide (AMol), especially in amounts of from 0.1 to 4% by weight, particularly preferably from 0.5 to 3% by weight, very particularly preferably in amounts of from 0.5 to 1.5% by weight.
When the polymer contains MAMol and AMol, the MAMol/AMol weight ratio is preferably in the range from 4:1 to 1:4, particularly preferably in the range from 2:1 to 1:2. Very particularly preferably MAMol is in excess compared with AMol, the weight ratio correspondingly being in the range from 4:1 to 1.1:1, especially in the range from 3:1 to 1.5:1.
As well as MAS, MAMol and AMol, the polymer may additionally contain methacrylamide (MAM), especially in amounts of from 0.1 to 4% by weight, preferably from 0.5 to 3% by weight, particularly preferably from 0.2 to 2% by weight.
The polymer can also contain acrylic acid. Preferably the total amount of the water-soluble compounds acrylic acid and AMol together is not more than 3% by weight, especially not more than 2.0% by weight, particularly preferably not more than 1.5% by weight.
Otherwise the polymer is preferably polymerized from main monomers so-called.
Preferably the polymer contains at least 60% by weight, particularly preferably at least 80% by weight, of units derived from main monomers (so-called) selected from C
1
to C
20
alkyl (meth)acrylates, vinyl esters of carboxylic acids containing up to 20 carbon atoms, vinyl aromatics with up to 20 carbon atoms, ethylenically unsaturated nitriles, vinyl halides, vinyl ethers of alcohols containing 1 to 10 carbon atoms, aliphatic hydrocarbons with 2 to 8 carbon atoms and 1 or 2 double bonds or mixtures thereof.
Useful examples are alkyl (meth)acrylates with a C
1
-C
10
-alkyl radical, such as methyl methacrylate, methyl acrylate, n-butyl acrylate, ethyl acrylate and 2-ethylhexyl acrylate.
Mixtures of alkyl (meth)acrylates are also suitable in particular.
Vinyl esters of carboxylic acids with 1 to 20 carbon atoms are for example vinyl laurate, vinyl stearate, vinyl propionate, vinyl versatate and vinyl acetate.
Useful vinyl aromatic compounds are vinyltoluene, &agr;- and p-methylstyrene, &agr;-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene and preferably styrene.
Examples of nitriles are acrylonitrile and methacrylonitrile.
Vinyl halides are chlorine-, fluorine- or bromine-substituted ethylenically unsaturated compounds, preferably vinyl chloride and vinylidene chloride.
Useful vinyl ethers include vinyl methyl ether and vinyl isobutyl ether. Preference is given to vinyl ethers of alcohols containing 1 to 4 carbon atoms.
Hydrocarbons with 2 to 8 carbon atoms and two olefinic double bonds are butadiene, isoprene and chloroprene; those with a double bond are for example ethene or propene.
Preferred main monomers are alkyl acrylates, styrene and especially mixtures of styrene and alkyl acrylates.
As well as these main monomers the polymer may contain further monomers, for example hydroxyl-containing monomers, especially C
1
-C
10
-hydroxyalkyl (meth)acrylates, dicarboxylic acids and their anhydrides or monoesters, for example maleic acid, fumaric acid and maleic anhydride or as constituents.
Preferred polymers are for example those which are completely polymerized from:
a) from 0.1 to 5% by weight of methacrylic acid (MAS)
b) from 0.1 to 5% by weight of methylolmethacrylamide (MaMol)
c) from 0.1 to 4% by weight of methylolacrylamide (AMol)
d) from 0 to 4% by weight of methacrylamide (MAM)
e) from 60% by weight to 99.7% by weight of the above-mentioned main monomers and
f) from 0 to 20% by weight of further monomers other than a) to e),
the weight percentages being based on the polymer.
Particularly preferred polymers are completely polymerized from:
a) from 0.5 to 3% by weight of MAS
b) from 1 to 4% by weight of MAMol
c) from 0.5 to 3% by weight of AMol
d) from 0.1 to 4% by weight of MAM
e) from 60 to 98.9% by weight of main monomers and
f) from 0 to 20% by weight of further monomers.
The aqueous dispersion is preferably prepared by emulsion polymerization; the polymers are therefore an emulsion polymer.
Emulsion polymerization is generally carried out using ionic and/or nonionic emulsifiers and/or protective colloids or stabilizers as surface-active compounds.
A detailed description of suitable protective colloids is given in Houben-Weyl, Methoden der organischen Chemie, Volume XIV/1, Makromolekulare Stoffe, Georg-Thieme-Verlag, Stuttgart, 1961, pages 411 to 420. Useful emulsifiers include anionic, cationic and also nonionic emulsifiers. Preferably the accompanying surface-active substances used are exclusively emulsifiers whose molecular weights, in contrast to protective colloids, are usually below 2000 g/mol. It will be appreciated that, when mixtures of surface-active substances are used, the individual components have to be compatible with each other, which is simple to verify by means of a few preliminary tests in cases of doubt. Preference is given to using anionic an
Claassen Peter
Leman Titus
Olfermann Kai
Schmidt-Thümmes Jürgen
Seyffer Hermann
BASF - Aktiengesellschaft
Kiliman Leszek B
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