GB1430174A - Process for beater-sizing apper - Google Patents

Abstract

1430174 Beater-sizing paper BASF AG 13 July 1973 [15 July 1972 22 Aug 1972] 33510/73 Heading D2B In a process for beater sizing paper, an aqueous polymer dispersion is added to the paper pulp, the dispersion being obtained by free radical polymerisation of at least one hydrophobic monomer in aqueous medium in the presence of a carboxyl containing emulsifier, and having an average particle size of less than 200 nm and a glass temperature of less than 70‹C. Preferably, the poylmer is formed from comonomers, at least one of which when polymerised alone produces a polymer having a high glass temperature, preferably 80‹C (referred to as a hard monomer), and at least one of which when polymerised alone produces a polymer having a low glass temperature, preferably less than 40‹C (referred to a soft monomer). Suitable hard monomers are styrene, α-methylstyrene, α-ethylstyrene, acrylonitrile, methacrylonitrile, vinyl chloride and vinylidene chloride. Suitable soft monomers are n-butyl acrylate, n-butyl methacrylate, ethylhexyl acrylate, cyclohexyl methacrylate, n-propyl acrylate, n-propyl methacrylate, butadiene, isoprene, ethylene, propylene, vinyl ethers, and vinyl esters such as vinyl stearate. Minor quantities (up to 5%) of methyl, ethyl and propyl acrylates may also be included. The polymer may also contain small amounts (less than 2%) of monomers having hydrophilic groups: e.g. acrylamide, methacrylamide, vinyl caprolactam, acrylic acid, methacrylic acid, vinyl pyrrolidone, vinyl carbazole, vinyl sulphonates, #-hydroxyethyl acrylate, #-hydroxypropyl acrylate, butanediol monoacrylate, vinylimadazole and alkylaiminoethyl acrylates. Other monomers mentioned in the examples are vinyl toluene, isopropyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, hexadecyl acrylate, ethylhexyl methacrylate, lauryl acrylate, and diisooctyl phthalate. The ratio of hard monomer to soft monomer is conveniently 80/20 to 20/80. The monomers are polymerised by the use of free radical initiators such as potassium peroxy disulphate, azoisobutyronitrile, lauroyl peroxide and hydrogen peroxide. Suitable carboxyl containing emulsifiers are organic and inorganic salts of the following: oleic acid, linolenic acid, stearic acid, isostearic acid, higher fatty acids, resin acids or their hydrogenation or disproportionation products, the reaction products of the monoene or diene synthesis of higher olefins with maleic acid derivatives, acids formed by the carbonylation of C 12-20 olefins (isofatty acids), the reaction products of fatty alcohols and fatty amines with cyclic anhydrides e.g. the reaction products of stearyl amine with maleic anhydride or phthalic anhydride, and the acrylation products of amino-acids such as glycine or methylglycine with fatty acids. Emulsifiers mentioned in the examples include rosin derivatives, sodium stearate, sodium oleate, octadeceryl succinic acid (disodium salt), the reaction product of cyclododecatriene-1, 5, 9 with 1 mole of maleic anhydride (disodium salt), triethanolamino oleate, acrylation product of methylglycine with stearic acid (potassium salt), tallow oil fatty acid (sodium salt or potassium salt), reaction product of anthracene with methacrylic acid (sodium salt), reaction product of maleic anhydride with octadecylamine (ammonium salt), carbonylation product of a C 6-20 α olefin mixture with carbon monooxide (sodium salt), triethanolamine salt of a product of maleic anhydride with stearylamine, and the Dielo-Alder reaction product of maleic anhydride with rosin (potassium salt). The emulsifier is preferably present in an amount of 1 to 20% by weight of the comonomers. The dispersion is added to the paper pulp in an amount of 0.5 to 10% of the dry weight of the pulp and the pH is preferably 5 to 9. Melamine formaldehyde resin sizing agents may also be added to the pulp, either mixed with the polymer dispersion or separately, preferably at a pH of 3 to 9. Suitable melamine formaldehvde resins include the condensation product of melamine and formaldehyde with a) aminoacetic acid, b) #-aminocapronic acid, c) o-aminobenzoic acid, d) sodium bisulphite, or e) methyl alcohol. Other additives which may be present in the pulp include 1) hydrophilic wax dispersions 2) cationally active compounds such as polyethylene imines, polyamido amines, and cross linked products of these compounds with epichlorohydrin, and reaction products of dicyano diamide, formaldehyde and urea 3) an anionic paper brightener and 4) china clay. The pulp may include the following pulps: bleached semibleached and unbleached sulphite, bleached sulphate, bleached birch, bleached beech, spruce and waste paper. Numerous examples are given describing in detail the process of the invention and the results.