AU672685B2

AU672685B2 - Copolymer produced in two stages

Info

Publication number: AU672685B2
Application number: AU61975/94A
Authority: AU
Inventors: Uwe Dittrich; Gerhard Schumacher; Alexander Zettl
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1993-05-12
Filing date: 1994-05-10
Publication date: 1996-10-10
Anticipated expiration: 2014-05-10
Also published as: EP0730061B1; JPH06329734A; DE59409636D1; EP0624607A1; EP0730061A2; DE4315881A1; EP0730061A3; AU6197594A; ES2153511T3; CN1098111A

Description

x~a~; F/UU/1 1 28/5/91 Regulation 3.2(2)

AUSTRALIA

Patents Act 1990 i i i I3 r i.

iE i f ii I 1

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: u r r s rr rr*r Invention Title: COPOLYMER PRODUCED IN TWO STAGES The following statement is a full description of this invention, including the best method of performing it known to us u*,r r r i **r ur,, uu~rr i O.Z, 0050/44029 SCopolvmer produced in two stages The present invention relates to a copolymer obtainable by polymerization (1st stage) of 1-99% by weight of a ionomer mixture A) of 50-100% by weight of at least one Ci-C3 6 -alkyl (meth)acrylate a), 0-40% by weight of at least one vinylaromatic of up to carbon atoms b), 0-30% by weight of at least one aliphatic diolefin of up to 8 carbon atoms c) and 0-40% by weight of at least one further monomer d", the amount by weight of b) and c) together being not more than 49% by weight, and subsequent polymerization (2nd stage), in the presence of the polymer obtained from of 1-99% by weight of a monomer mixture B) of 50-100% by weight of a mixture of at least one monomer b) and at least one monomer c), 0-40% by weight of at least one monomer a) and 0-40% by weight of at least one monomer d), the percentages by weight ot the monomer mixtures A) and B) being based on the sum A) B).

The present invention furthermore relates to adhesives and coating materials containing the copolymer produced in at least two stages.

Requirements which copolymers have to meet when used as adhesives, for example contact adhesives, and also as coating materials are in particular good adhesion to surfaces and good internal strength (cohesion), in order to achieve, for example, a very strong adhesive .bond. These two requirements can scarcely be equally well fulfilled since many measures which, for example, produce good cohesion have an adverse effect on the adhesion. For example, the skilled worker knows that the cohesion increases with increasing molecular weight but the adhesion simultaneously deteriorates to a corresponding extent.

Both polyacrylates and copolymers based on styrene and butadiene serve as a polymer base for 4 2 O.Z. 0050/44029 adhesives.- In order to improve the adhesion, tackifiers are generally also added to the adhesives.

US-A-4 438 232 discloses a contact adhesive based on a copolymer of styrene, butadiene and alkyl acrylates.

This copolymer is said to have good cohesion and also improved adhesion. However, the adhesion and cohesion of this copolymer must be further improved for many applications.

It is an object of the present invention to provide copolymers which, when used as adhesives, have good adhesion and good cohesion. 2 We have found that this object is achieved by the at least two-stage copolymer defined at the outset, and adhesives, coating materials or binders containing this copolymer.

The copolymer defined at the outset is produced in at least two stages, preferably in two stages. In the first stage, a monomer mixture A) which preferably consists of 70-100% by weight of at least one monomer a), 0-10% by weight of at least one monomer b), by weight of at least one monomer c) and 0-30% by weight of at least one monomer d) Sis polymerized.

S 25 The monomer mixture A) particularly preferably consists of 70-100% by weight of at least one monomer a), by weight of at least one monomer b) and 0-30% by weight of at least one monomer d).

The monomer mixture B) of the 2nd stage is then polyserized in the presence of the polymer obtained in the first stage.

The monomer mixture B) of the second stage preferably consists of 70-100% by weight of a mixture of at least one monomer b) and at least one monomer c), 0-10% by weight of at least one monomer a) and The monomer mixture B) particularly preferably tins I-~ 9c- 3 O.Z. 0050/44029 Ir I consists of 90-100% by weight of a mixture of at least one monomer b) and at least one monomer c), by weight of at least one monomer a) and 0-5% by weight of at least one monomer d).

The weight ratio of the monomers b) to c) in the monomer mixture B) is preferably from 10 1 to 1 particularly preferably from 1 0.5 to 1 particularly preferably from 1 1.5 to 1 The amount by weight of monomer mixture A) is preferably from 2 to 50, particularly preferably from 2 to 20, by weight, and that of B) is preferably from to 98, particularly preferably from 98 to 80, by weight, based on the sum of A) B).

Monomers a) are preferably C 1 -C.-alkyl (meth)acrylates. Examples are methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate. C-C-Alkyl acrylates are very par- 20 ticularly preferred.

Monomers b) are, for example, a-methylstyrene, pmethylstyrene and preferably styrene.

Examples of monomers c) are isoprene and preferably butadiene.

25 Further monomers d) may be, for example, (meth)acrylonitrile, C 1

-C

16 -hydroxyalkyl (meth)acrylates, vinyl ethers of carboxylic acids of 1 to 20 carbon atoms, such as vinyl acetate, unsaturated anhydrides of, preferably, 4 or 5 carbon atoms, such as maleic anhydride or itaconic 30 anhydride, or unsaturated carboxylic acids of, preferably, 3 to 5 carbon atoms, such as (meth)acrylic acid, itaconic acid, maleic acid or fumaric acid.

Particularly preferred monomers d) are unsaturated carboxylic acids_- 35 The at least two-stage copolymer is preferably prepared by emulsion polymerization. The monomer mixture A) is polymerized in emulsion in the 1st stage, with the result that an aqueous dispersion of the corresponding polymer is obtained.

,r r r .r r rr o r r ur u* rurr r r

YY

I**Y

Oi

I

L K 7 t 4 O.Z. 0050/44029 The monomers of the monomer mixture B) can then be added to this aqueous dispersion in the 2nd stage and polymerized as in the case of A).

In the polymerization in the individual stages, the monomer mixtures A) and B) can be initially taken or added all at once; however, the addition of the monomers in the individual stages may also be effected by the feed method, if required a part of the monomers being initially taken.

The polymerization of the monomer mixture B) is started only when the residual monomer content in the polymerization of the monomer 'mixture A) is preferably less than 10, particularly preferably less than 5, very particularly preferably less than 1, by weight, based on monomer mixture A).

The emulsion polymerization in the individual stages can be carried out in a conventional manner in the presence of a water-soluble initiator and an emulsifier at, preferably, from 30 to 95 0

C.

20 Examples of suitable initiators are sodium persulfate, potassium persulfate, ammonium persulfate, tert-butyl hydroperoxide, water-soluble azo compounds and redox initiators.

Examples of emulsifiers used are alkali metal salts of relatively long-chain fatty acids, alkylsulfates, alkylaulfonates, alkylated arylsulfonates and alkylated diphenyl. ether sulfonates. Other suitable emulsifiers are reaction products of alkylene oxides, in particular ethylene oxide or propylene oxide, with fatty 30 alcohols, fatty acids or phenol or alkylphenols.

The finally obtained aqueous dispersion of the novel copolymer preferably has a solids content of from 20 to 70% by weight.

The novel copolymer or the aqueous dispersion of the copolymer obtained in the emulsion polymerization is suitable for all uses where good adhesion of polymers to substrate surfaces and good cohesion, ie. internal strength, of polymers are desired.

The novel copolymer furthermore exhibits very

*O

001 *Y I) u~oa r** *uu uu i OOP li

II

iI

L

5 O.Z. 0050/44029 good penetration behavior and is therefore also suitable as a contact adhesive for coating paper, in particular labels. Poor penetration behavior is understood as meaning the penetration of the adhesive from the coated to the uncoated side.

Furthermore, packaging adhesive tapes, in particular those consisting of plastic, which are coated with the novel copolymer cive rise, during unwinding from the reel, to a low level of unwind noises, which otherwise lead to high noise pollution in industrial packaging plants.

Such uses are, for example, uses as an adhesive, for example also as a contact adhesive, or as a coating material of any type. Examples of the latter are surface coatings, leather coatings, textile coatings, backing coatings for carpeting and paper coating slip.

The copolymers are also suitable for the coating of, or as binders for, nonwovens, for example needled nonwovens, and for applications in building chemistry.

Nonwovens, in particular needled nonwovens, which are compacted using a binder containing a novel copolymer, exhibit excellent abrasion remiptance and resistance to wear. This is evident, for example, in the measurement of the following properties of a floor covering consisting of a needled nonwoven: wheelchair test (DIN 54 324) and Lisson treadwheel test (DIN 54 322).- The binders are suitable for nonwovens based on, for example, polypropylene, polyester, polyamide, natural fibers and any blends of these fibers. 'Ymn these binders are used, conventional additives, for example thickeners and/or fillers, may be added.

The substrates to be adhesively bonded or to be coated may be, for example, paper, wood, textiles, metal, plastics, concrete, etc.

EXAMPLES

Emulsion polymer A (for comparison) The monomers (cf. Table 1) were polymerized at

C..

.4CC

C

I

II'

lli4 3 6 O.Z. 0050/44029 j I;h ;i 77 0 C in emulsion using sodium persulfate as an initiator and an aliphatic sodium sulfonate as an emulsifier by the feed method (monomers fed in over 6 hours and subsequent polymerization carried out for 6 hours).

Emulsion polymers B to D (two-stage) The monomers of stage 1 were polymerized in the vessel in the presence of the abovementioned initiator and emulsifier for 15 minutes.

Thereafter, the monomers of the 2nd stage were polymerized in the presence of the 1st stage, as described under A.

The parts by weight of the monomers are shown in Table 1.

C

.04*

C

C*

t^ 1 A1 1 7 O.Z. 0050/44029 TABLE 1 Composition of the emulsion polymers I A lB C D First stage Butyl acrylate 0 3 5 10 Itaconic acid 0 0.6 0.6 0.6 Second stage Butadiene 69.8 66.8 64.8 59.8 Styrene 28 28 28 28 tert-Dodecyl mercaptan 2.1 2.1 2.1 2.1 Itaconic acid 2.2 1.6 1.6 1.6 r r i r i f 1 j~ i i I:j

I

Testing of performance characteristics In order to test the performance characteristics, the emulsions obtained were applied to label paper 25 (80 g/m 2 from Hering) with a knife coater at a weight per unit area of about 20 g/m and the coated films were dried for 3 minutes at 90 0 C in a through-circulation dryer. The coated films were then cut into 2 cm wide test strips.

30 In order to determine the shear strength, the adhesive strips were stuck to a chromium-plated V2A stainless steel test sheet over a bonded area of 1 x 0.5 inch, rolled on once with a roller weighing 1 kg, stored for 20 minutes and then loaded with a 1 kg weight 35 by suspension. The measure of the shear strength was the time taken for the weight to fall; the mean of 5 measurements was calculated in each case (corresponding to test method PSTC 7).

The shear strength was determined at 25 0

C.

In order to determine the quickstick value, a loop was formed from a 17.5 cm long and 2 cm wide test strip by clamping both ends in the jaws of a tensile test machine, and said loop was then brought into contact with a chromium-plated steel surface at a rate of 30 cm/min (lowering of the loop onto the chromium-plated steel i 8 O.Z. 0050/44029

I

r o r e ~r sheet). After contact over the complete area, the loop is immediately pulled off again, and the maximum forci is determined in N/2 cm. as a measure of the quickstick value (loop value, tack) (corresponding to test method PSTC The results are shown in Table 2.

TABLE 2 Test results Emulsion Parts by weight Quickstick Shear strength polymer of n-butyl acrylate A 0 2 N/2 cm >72 h B 3 10 N/2 cm >72 h C 5 13 N/2 cm >72 h D 10 20 N/2 cm >72 h Test results for one-stage styrene/butadiene/n- 20 butyl acrylate emulsion polymers from US-A-4 438 232 are shown for comparison.

Emulsion by weight Quickstick Shear strength polymer of n-butyl acrylate E 1 0 5.2 N/2 cm* >48 h E 3 5 4.2 N/2 cm >48 b 30 E 4 20 5.7 N/2 cm >48 h *Values were converted from data in US-A-4 438 232 The quickstick and the peal strength on cardboard were also tested. The peel strength test was carried out as described above for the shear strength, the adhesive strip being stuck onto cardboard and peeled off at an angle of 1800 from the test surface.

Emulsion polymer Quickstick Peel strength C 2.7 6.1 2nd stage of only 0.8 0.2 Mixture of 1st stage and 2nd stage of 1 0.9

I

SI

ii r r r r r s rr r*r ror oru~i r l _i i c f//I 9 O.Z. 0050/44029 Emulsion polymer having the composition of the second stage of C Mixture of two emulsion polymers with, in each case, the compositions of the first and second stages of C in the ratio of the stages as in C In addition, the tests according to Table 2 were repeated by determining the quickstick values on cardboard.

For comparison, emulsion polymer E3 was prepared and the butyl acrylate content BA was varied with an otherwise identical composition.

r 1 r{ I I 0*.

r SO by weight Emulsion Stages. Quickstick of BA polymer N/2 cm 3 B 2 1.9 5 C 2 2.8 D 2 3 E3 1 0.9 5 E3 1 1.3 10 E3 1 1.2 Use examples for paper coating compositions One problem which concerns printers, in particular irt offset printing, is mottling. Oviing to mottling, the print quality suffers. It occurs as a result of different ink acceptance by the paper. The relationships between paper quality and mottling tendency are still unclear to date. However, it appears that the coating slips of coated papers are particularly important. It has now been found that papers which are coated with paper coating compositions which contain the novel dispersion or the novel copolymer as binder exhibit partiularly good printability (little mottling).

I

it i;( i ir .i i YZ i 1

I

t

I

r r r r o r r r ip 10 o.Z. 0050/44029 EXAMPLE 1 Preparation of a novel polymer dispersion based on styrene/butadiene with initially taken butyl acrylate Initially taken mixture: 21.9 kg of demineralized water 0.50 kg of sodium laurylsulfate, 10 strength in water 4.35 kg of n-butyl acrylate kg of styrene 0.15 kg of acrylic acid 1.05 kg of Feed 2 Feed 1 26.75 kg of demineralized water 17.5 kg of butadiene 31.0 kg of styrene 1.5 kg of acrylic acid 0.5 kg of tert-doeecyl mercaptan 2.50 kg of sodium laurylsulfate, 15 strength in water Feed 2 0.4 kg of sodium, persulfate 20 4.85 kg of demineralized water The initially taken mixture was heated to 85 0

C

and prepolymerization was carried out for 15 minutes.

Thereafter, the remainder of Feed 1 was added in the course of 5 hours and, beginning at the same time as Feed 25 1, Feed 2 was introduced in the course of 5.5 hours.

Polymerization was then completed in the course cf 2 hours at 85 0 C. A dispersion having a particle size (Malvern Autosizer) of 176 nm and a solids content of was obtained. The glass transition temperature was 22 0

C.

EXAMPLE 2 Preparation of a polymer dispersion based on butadiene without initially taken butyl acrylate inot according to the invention) 25 Qi I

I,

11 O.Z. 0050/440; Initially taken mixture: 19.4 kg of demineralized water 0.25 kg of sodium laurylsulfate, 10 strength in water 3.88 kg of Feed 1 1.05 kg of Feed 2

C

Feed 1 24.25 kg of demineralized water 17.5 kg of butadiene 31.0 kg of styrene 1.5 kg of acrylic acid kg of tert-dodecyl mercaptan 2.75 kg of sodium laurylsulfate, 15 strength in water Feed 2 0.4 kg of sodium persulfate 4.85 kg of demineralized water The initially taken mixture was heated to 85 0

C

and prepolymerization was carried out for 15 minutes.

Thereafter, the remainder of Feed 1 was added in the course of 5 hours and, beginning at the same time as Feed 20 1, Feed 2 was introduced in the course of 5.5 hours.

Polymerization was then completed in the course of 2 hours at 85°C. A dispersion having a particle size (Malvern Autosizer) of 170 nm and a solids content of was obtained. The glass transition temperature was 17 0

C.

EXAMPLE 3 Preparation of a polymer dispersion based on a terpolymer of styrene, butadiene and butyl acrylate (not according to the invention) Initially taken mixture: 19.4 kg of demineralized water 0.25 kg of sodium laurylsulfate, 10 strength in water 3.88 kg of Feed 1 1.05 kg of Feed 2 8 1 -i i I 1a 1 i

I

H s it it m 1 "I me perce Tages uy Wt. ot tne monomer mixtures A) and B) being based on the sum A) B).

1, /2 12 O.Z. 0050/44029 Feed 1 24.25 kg of demineralized water 13.5 kg of butadiene kg of n-butyl acrylate 30.0 kg of styrene kg of acrylic acid kg of tert-dodecyl mercaptan 2.75 kg of sodium laurylsulfate, 15 strength in water Feed 2 0.4 kg of sodium persulfate 4.75 kg of demineralized water The initially taken mixture was heated to and prepolymerization was carried out for 15 minutes.

i: *Thereafter, the remainder of Feed 1 was added in the 15 course of 5 hours and, beginning at the same time as Feed 1, Feed 2 was introduced in the course of 5.5 hours.

Polymerization was then completed in the course of 2 hours at 85°C. A dispersion having a particle size (Malvern Autosizer) of 170 nm and a solids content of 50 was obtained. The glass transition temperature was 21 0

C.

The dispersions prepared in the examples were used as binders in a paper coating composition having the following composition: 25 60 parts of finely divided chalk parts of finely divided clay I 1 part of a sodium salt of a polyacrylic acid having i a molecular weight of 4000 (Polysalz from BASF) 12 parts of binder dispersion (from Examples 1 to 3) Solids content: 66 by weight pH: from 8.5 to 9 (established with NaOH) The base paper used was a wood-free coating base paper having a basis weight of 90 g/m 2 The coating composition was applied on both sides, in each case in an amount of 13 g/m, on a pilot coating machine (application method: roller, metering method: blade) at a speed of 1000 m/min. The paper web was brought to a Pr

IN

IWO

i .o I I 13 O.Z. 0050/44029 moisture content of 5.5 by means of an IR drying unit and by air drying.

The paper web was calendered by a single pass through a super calender. The nip pressure was 250 kN/m, the web speed was 300 m/min and the temperature was 80 0

C.

In order to assess the printability, mottle scan values were determined with the aid of a Tobias tester.

(The method of measurement is described in: Philipp E.

Tobias et al., Tappie Journal, Vol. 72, No. 5, May 1989.) The mottle scan values were determined in a colored area which was printed with an ink coverage of 50 of the maximum ink coverage of the color cyan on a 4-color offset printing press by. the sheet-fed offset printing process. High mottle scan values indicate poor printability.

j r j i i

I

i i, i ii t i j f i 1 i j r

I

*4r Table Binder Mottle scan value Example 1 425 Example 2 623 Example 3 595 20 /'i rl t i i t t'l i I i i'' iri i r I j C: j .1.

Claims

70-100% by weight of a mixture of at least one monomer b) and at least one monomer cd), the percentag0-10% by weight of at least one monomer a) and) and B) being based on the 0-30% by weight of at least one monomer d). T-I- q 0-30% bon 010 ywih fa es n ooe Both polyacrylatet and copolyalers asea on styrene and butadiene serve as a polymer base for 3. The adhesive tape as claimed in Claim 1, wherein the weight ratio of the 4 monomers b) to c) in the monomer mixture B) is from 10:1 to 1 4. The adhesive tape as claimed in Claim 1, wherein the copolymer is prepared by the emulsion polymerization of the monomer mixtures A) and B). The adhesive tape as claimed in Claim 1, wherein in monomer mixtures and monomers a) are selected from the group consisting of Ci-C 8 -alkyl (meth) acrylates; monomers b) are a-methylstyrene, p-methyl-styrene and styrene; monomers c) are isoprene and butadiene; and monomers d) are selected from the group consisting of (meth) acrylonitrile, C1- C 16 -hydroxyalkyl (meth) acrylates, vinyl esters of carboxylic acids of 1 to carbon atoms, unsaturated anhydrides and unsaturated carboxylic acids. 6. A process of offset printing, comprising: printing a pattern on a substrate from a printing paper coated with a coating composition containing, as a binder, a copolymer obtained by polymerizing in a first stage: 2 to 50% by wt. of a monomer mixture of 50-100% by wt. of at least one Ci-Ce 1 -alkyl (meth) acrylate a), 0-40% by wt. of at least one vinylaromatic of up to 20 carbon atoms b), 0-30% by wt. of at least one aliphatic diolefin of up to 8 carbon atoms c) and 0-40% by wt. of at least one further monomer d), the amount by wt. of b) and c) together being not more than 49% by wt., and subsequently polymerizing, in a second stage, in the presence of the polymer obtained from monomer mixture of 98 to 50% by wt. of a monomer mixture of 50-100% by wt. of a mixture of a least one monomer b) and at least one monomer c), S: 0-40% by weight of at least one monomer a) and 0-40% by wt. of at least one monomer d), the percentages by wt. of the monomer mixtures A) and B) being based on the sum B). a 1 g ?s ii^ _I i ii ii i i i i i i i i F j 16 7. The process as claimed in Claim 6, wherein the monomer mixture A) consists of 70-100% by weight of at least one monomer a), 0-10% by weight of at least one monomer b), by weight of at least one monomer and 0-30% by weight of at least one monomer d) and the monomer mixture B) consists of 70-100% by weight of a mixture of at least one monomer b) and at least one monomer c), 0-10% by weight of at least one monomer a) and 0-30% by weight of at least one monomer d). 8. The process as claimed in Claim 6, wherein the weight ration of the monomers b) to c) in the monomer mixture B) is from 10:1 to 1:10. 9. Th process as claimed in Claim 6, wherein the copolymer is prepared by the emulsion polymerization of the monomer mixtures A) and B). 10. The process as claimed in Claim 6, wherein in monomer mixtures and monomers a) are selected from the group consisting of C 1 -C 8 -alkyl (meth) acrylates; monomers b) are a-methylstyrene, p-methyl-styrene and styrene; monomers c) are isoprene and butadiene; and monomers d) are selected from the group consisting of (meth) acrylonitrile, C 1 C 16 -hydroxyalkyl (meth) acrylates, vinyl esters of carboxylic acids of 1 to carbon atoms, unsaturated anhydrides and saturated carboxylic acids. i .4 *r a .4 a a .44. 4 *r C 4. 4 a DATED this 1st day of July 1996 BASF AKTIENGESELLSCHAFT WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA ,CG:JGC:KR Doc 7 AU6197594.WPC VI i 140w L I nh I 1. O.Z. 0050/44029 Abstract of the Disclosure: A copolymer is obtainable by polymerization (1st stage) of 1-99% by weight of a monomer mixture A) of 50-100% by weight of at least one C 1 -C 6 -alkyl (meth)- acrylate a), 0-40% by weight of at least one vinylaromatic of up to carbon atoms b), 0-30% by weight of at least one nonaromatic diolefin of up to 8 carbon atoms c) and 0-40% by weight of at least one further monomer d), the amount by weight of b) and c) together being not more than 49% by weight, and subsequent polymerization (2nd stage), in the presence of the polymer obtained from of 1-99% by weight of a monomer mixture B) of 50-100% by weight of a mixture of at least one monomer b) and at least one monomer c), 0-40% by weight of at least one monomer a) and 0-40% by weight of at least one monomer d), the percentages by weight of the monomer mixtures A) and B) being based on the copolymer produced in at least two stages. S S I U o I