FI68855C - COMPOSITION FOR THE UNION OF SAOSOM PAPER CARDBOARD DYLIKA - Google Patents

Description

r, ANNOUNCEMENT Q ®181ηΙ B 11 UTLÄGG NI NGSSKRIFT 68 85 5 c (45) Patent issued by Li 11 1985

Patent n,;: - c! Delnt ^ ^ ^ (51) Kv.lk.7int.Ci.4 CL 25/10, 9 / Ο8, V 'D 21 H 1/28 FINLAND— FINLAND (21) Patent application - Patentansdknlng 772925 (22) Hakemlspilvä - Antöknlngsdag 04.1 0.77 (^) (23) Start date - Glltighetsdag 04.1 0.77 (41) Become public - Blivit offend lg 07.04.78

National Board of Patents and Registration of Finland / 444 Date of the spectacle competition and the publication of the hearing— ·>. λ.7 no

Patent- och registerstyreisen 'Ansökan utlagd och utl.skriften publlcerad ji .u / .op (32) (33) (31) Privilege claimed - Begärd priority 06.1 0.76 United Kingdom and Storbr itannien (GB) 41606/76 (71) Doverstrand Limited, Temple Fields, Harlow, Essex, United Kingdom-Storbr i Tann i en (GB) (72) Basil Alexander Ripley-Duggan, Harlow, Essex, Mohinder Singh Mahil,

Harlow, Essex, Great Britain-Storbritannien (GB) (74) Berggren Oy Ab (54) A composition for coating paper, board and similar substrates - The present invention relates to a mixture of paper, board and to coat such substrates.

For the sake of simplicity, this patent specification will refer to paper as a coating substrate, as well as paper coating and paper coating compositions. It is to be understood that in the context of this specification, these terms include not only paper but also paperboard and the like, especially those composed of natural cellulosic fibers.

The use of high polymeric latexes as pigment binders in paper coating compositions is known in the art, and a particularly useful group of high polymeric latexes is that which includes copolymers of styrene and butadiene. These copolymers usually contain other copolymerizable monomer units, 2,685,85 selected, for example, from the group consisting of ethylenically unsaturated carboxylic acids such as acrylic, methacrylic, fumaric and itaconic acid, acrylonitrile, acrylic and other acrylic acid esters.

High polymer latices of this type are often considered superior to other high polymer latices for use as paper coating binders because they provide a satisfactory level of performance over a number of important properties in paper coatings, both in terms of the coating methods used to coat the substrate and the resulting product. Properties that are important in the coating process include e.g. chemical stability that allows latex to be transported and pumped and pigment-containing coating compositions to be deposited on a wide variety of paper, board and similar substrates at the high coating rates typical of current coating technology, without, for example, deactivation, accumulation of residues taken on the coating machinery.

Properties that are important for the coated substrate include e.g. surface strength both dry and wet, a good balance between ink ink absorption and retention, and, if necessary, the ability to achieve a relatively high gloss on the surface of the coated substrate, for example by calendering.

"Surface strength" means the ability of a coated substrate to withstand, during printing processes, the deposition of viscous printing inks on the surface of the coated substrate by high-speed printing presses. Insufficient surface strength manifests itself as a breakage of the coating during the printing process.

Although sufficient surface strength can often be achieved by using styrene / butadiene copolymer latices known in the art as pigment binders, this has generally only been achieved by using a relatively high proportion of these latexes in paper coating compositions, resulting in increased raw material costs for these coatings.

It would be desirable to provide latices that provide significantly better dry and wet surface strength than previously known latexes, either to allow higher weight rates or to allow the amount of latex used as a binder to be reduced relative to the amount of pigment in the coating compositions.

According to one aspect of the present invention, there is provided a latex of a copolymer comprising 35 to 65 parts by weight of copolymerized styrene units, 30 to 60 parts by weight of copolymerized 1,3-butadiene units, 2 to 25 parts by weight of copolymerized acrylic per 100 parts by weight. -nitrile or methacrylonitrile units, 0.25 to 10 parts by weight of copolymerized hydroxyalkyl monomer units (defined below), and 0 to 5 parts by weight of copolymerized units of copolymerizable unsaturated carboxylic acid.

The term "hydroxyalkyl monomer" is used herein to mean an ethylenically unsaturated monomer capable of copolymerizing with styrene and / or butadiene and containing a group of the general formula -CR 1 -OH, wherein R 2 and R 2 may each be a hydrogen atom or a C ^^ lkyyliryhmä. Examples of such hydroxyl-containing monomers are e.g. hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, N-methylol-acrylamide, N-t-butyl-N-methylolacrylamide, N-octyl-N-methylol-acyl-ethoxyethylamine derivative, hydroxy-methylol-diacetoniacryoxide

The latex copolymer of the invention preferably contains 40 to 60 parts by weight of copolymerized styrene units, 35 to 55 parts by weight of copolymerized 1,3-butadiene units, 4 to 15 parts by weight of copolymerized acrylonitrile or methacrylics, 1 to 15 parts by weight of copolymer. parts of copolymerized hydroxyalkyl monomer units and 1-3 parts by weight of copolymerized unsaturated copolymerizable carboxylic acid units.

According to the invention, it is possible that up to 20% of other copolymerizable monomers, including acrylic, methacrylic, fumaric, maleic and itaconic acid esters, substituted styrenes such as alpha-methylstyrene, vinyltoluene, vinyltoluene, can be included in the copolymer in addition to the above-mentioned monomers. 4,685,55 vinylidene chloride, isoprene, 2,3-dimethylbutadiene, piperylene, acrylamide and methacrylamide.

Those copolymerizable carboxylic acids which can be used in the latex according to the invention include e.g. acrylic, meta-acrylic, fumaric and itaconic acids, of which acrylic acids are generally preferred.

An essential feature of the latex according to the invention is that a hydroxyalkyl monomer with either acxylyl nitrile or methacrylonitrile is used to prepare the copolymer, which copolymer is preferably prepared by conventional emulsion polymerization methods. It has been found that in some cases a small improvement in the surface strength of paper coating compositions can be achieved by using carboxylated styrene-butadiene copolymer latexes containing either hydroxyalkyl monomer and / or acrylonitrile copolymerized units as binders, but this improvement. surface strength improvement achievable using latexes. In addition, paper coating compositions based on a carboxylated styrene / butadiene acrylonitrile-copolymer latex that does not contain a hydroxyalkyl monomer have a particularly high ink absorption capacity, which, although useful in some contexts, is generally not desirable.

The copolymer latexes according to the invention make it possible to formulate paper coating compositions so as to have significantly better surface strength as well as ink absorbency properties, which can vary quite widely, depending on the ratio of copolymerized hydroxyalkyl monomer units to acrylonitrile nitrile or methacrylonitrile or methacrylonitrile. It should be noted that the absorbency of the ink can also be adjusted by other adjustable parameters of the paper coating compositions, e.g. the average particle diameter of the latex and the relative number of copolymerized butadiene units.

The copolymer latexes of the invention may be prepared by conventional emulsion polymerization methods, and these latexes may contain, in addition to monomers, other conventional ingredients such as surfactants, polymer foundation initiators, molecular weight modifiers, dispersants, and bulking agents. Suitable polymerization methods and ingredients are known to those skilled in the art of emulsion polymerization.

According to another aspect of the present invention, there is provided a latex according to claim 1, characterized in that the relative amount of copolymerized styrene units is 40 to 60 parts by weight. In general, the coating compositions of the invention contain a copolymer latex of the type described above as a binder for pigments such as, for example, kaolin or an off-white dispersion, and may further contain dispersing agents such as tetrasodium pyrophosphate, carboxylate alkaloids, water soluble colloids and / or thickening agents such as sodium polyacrylate. , thermosetting resins such as melamine formaldehyde condensates and other materials known to those skilled in the art of paper coating. In addition, the high polymer latices of the invention need not be the sole pigment binder contained in the paper coating composition, but the composition may contain other binders such as, for example, previously known high polymer latexes, starch, casein, polyvinyl alcohol, and the like. In order to obtain the full technical or economic advantages of the latices according to the invention, the relative amount of these additional binders must be small and should preferably be omitted.

The invention will now be explained in more detail by means of the following examples. Examples 1-5

A series of latices were prepared by emulsion polymerization, using the monomer compositions of Table 1.

These latexes were used as binders in pigment coating compositions using the following composition: 6 68855

Parts by weight (dry solids) of "Dinkie" A-kaolin 100.00

Tetrasodium pyrophosphate 0.25

Sodium polyacrylate 0.10

Sodium hydroxide 0.10

Sodium carboxymethylcellulose 0.50

Latex 7.00

Water with a total solids content of 50.0%

Ammonia ad pH 8.5 The coating compositions thus obtained were manually layered with a Mayer rod on an air scraper-coating grade base paper having a Cobb value of approximately 25 so that the coating weighed 12 g / m 3, air-dried for 3 hours and drying was completed by contact With a drum heated to 110 ° C for 2 minutes. The coated papers were then conditioned at 23 ° C and 50% relative humidity and then supercalendered in 5 nips at 60 ° C.

The test results are shown in Table 1.

Table 1 _Latex n; o_

Monomers 12345

Butadiene 47 47 47 47 47

Styrene 51 44 42 42 40

Acrylic acid 22222

Acrylonitrile 05577

Hydroxyethyl acrylate 02424 I.G.T surface strength 58 80 83 77 79 Wet surface strength 60 81 80 75 76

The superiority of both dry and wet surface strength with latices 2-5 containing acrylonitrile and hydroxyethyl acrylate over latex 1 is obvious.

Examples 6-19

A series of latexes were prepared by emulsion polymerization using the monomer compositions of Table 2 7 68855. These latices were used as binders in pigment coating compositions using the following coating composition.

Parts by weight (dry solids) of "Dinkie" A-kaolin 100.00

Tetrasodium pyrophosphate 0.25

Sodium polyacrylate 0.10

Sodium hydroxide 0.10

Sodium carboxymethylcellulose 0.50

Latex 8.00

Ammonia gives pH 9

Water to a total solids content of 50% These coatings were deposited with a metal wire wrapped rod to a coating weight of 12 g / m 2 on a moderately bonded blister-free base paper (Reed Aerocoat), air dried for 3 hours at room temperature and dried in a pressure polisher at 110 ° C for 2 minutes. The coated papers were then calendered between rolls at 70 ° C in four nips with a line weight of 89 kg / cm, and finally conditioned at 23 ° C and 50% relative humidity.

The dry surface strength of the coatings was then measured with an IGT printability tester Type AC2, using IPI tack grade No. 5 ink, and the results are shown in the last column of Table 2.

In Table 2, latex numbers 6-11 (ml) are not in accordance with the present invention and are included for comparison. Latex numbers 12-19 represent latices prepared in accordance with the present invention. It is clear that latices 12-19 (ml) have significantly better surface strength than reference latices 6-11 (ml).

8 68855

Latex Butadiene Styrene Nitrile Acrylic Hydroxyalkyl IGT surface acid limonone strength 6 45 53 0 2 0 100 7 49 47 0 2 2 HEMA 97 8 49 47 0 2 2 HEA 102 9 47 49 0 2 2 MoAMd 103 10 47 47 0 2 4 HEA 106 11 47 41 10 2 0 104 12 47 42 7 2 2 HEA 135 13 47 37 10 2 4 HEA 133 14 47 39 10 22 HEMA 122 15 47 42 5 2 4 HEMA 135 16 47 44 5 MAN 2 2 HEA 113 17 47 39 10 22 MoAMd 113 18 47 44 5 2 2 HPMA 111 19 47 44 5 2 2 HPA 108

In Table 2, the column headed "nitrile" indicates the amount of acrylonitrile, except for latex No. 16 where methacrylonitrile (MAN) was used.

The abbreviations used in Table 2 have the following meanings: HEA 2-hydroxyethyl acrylate HPA 2-hydroxypropyl acrylate HEMA 2-hydroxyethyl methacrylate HPMA 2-hydroxypropyl methacrylate

MoAMd N-methylolacrylamide MAN methacrylonitrile

Claims (12)

1. A composition for coating paper, cardboard and such substrates containing at least one pigment and aqueous dispersion of a copolymer latex which binds it, characterized in that the copolymer latex contains per 100 parts by weight 35 to 65 parts by weight of copolymer controlled units, 30 to 60 parts by weight. copolymerized 1,3-butadiene units, 2-25 parts by weight of copolymerized acrylonitrile or methacrylonitrile units, 0.25-10 parts by weight of copolymerized units of a hydroxyalkyl monomer copolymerizable with styrene and / or butadiene and containing the -CR OH, wherein and R R represents hydrogen or a -CC₂-alkyl group, and 0-5 parts by weight of copolymerized units of a copolymerizable unsaturated carboxylic acid. Composition according to claim 1, characterized in that the proportion of copolymerized control units in the latex copolymer is 40-60 parts by weight. Composition according to claim 1 or 2, characterized in that the proportion of copolymerized 1,3-butadiene units in the latex copolymer is 35-55 parts by weight. 4. A composition according to any one of claims 1-3, characterized in that the proportion of copolymerized acrylonitrile or methacrylonitrile units in the latex copolymer is 4-15 parts by weight. 5. Composition according to any of the preceding claims, characterized in that the proportion of copolymerized hydroxyalkyl monomer units in the latex copolymer is 1-5 parts by weight. 6. Composition according to any of the preceding claims, characterized in that the proportion of copolymerized unsaturated carboxylic acid units in the latex copolymer is 1-3 parts by weight. Composition according to any of the preceding claims, characterized in that the copolymer contains up to 20 parts by weight one or more other copolymerizable monomers.