EP1149121A1

EP1149121A1 - Aqueous monoconstituent system of a polymer with acetal or aldehyde function

Info

Publication number: EP1149121A1
Application number: EP99958323A
Authority: EP
Inventors: Christophe Verge; Isabelle Betremieux; Karine Loyen; Christophe Soares; Bernadette Charleux; Jean-Pierre Vairon
Original assignee: Atofina SA
Current assignee: Arkema France SA
Priority date: 1998-12-16
Filing date: 1999-12-14
Publication date: 2001-10-31
Also published as: CA2355693A1; AU1570500A; WO2000035979A1; JP2003517499A; FR2787458A1

Abstract

The invention concerns a monoconstituent system based on polymer of size ranging between 50 and 500 nm crosslinking at room temperature during the film formation process. The crosslinking is obtained by the presence of a hydrated acetal and/or an aldehyde function which are self-crosslinking in an acid medium.

Description

SINGLE-COMPONENT AQUEOUS SYSTEM OF AN ACETAL OR ALDEHYDE FUNCTIONAL POLYMER

The invention relates to the field of aqueous crosslinking dispersions and in particular to the field of aqueous crosslinking dispersions at ambient temperature at the time of filming without the intervention of external agents.

These dispersions, generally designated by latex, are used in the coating industries, in particular in paints, adhesives, paper, leather, textiles and inks.

In general, the film-forming dispersions used in the industries described above contain particles of polymers as binders. This requires in most cases a post-crosslinking intended to improve the properties of the coatings obtained, in particular the resistance to solvents, the mechanical properties and the reduction of surface tack.

The crosslinking step must be adapted to the conditions of implementation and the field of application.

Often post-crosslinking causes certain problems such as yellowing and degradation of the film, or even an additional production cost.

These problems can be avoided by crosslinking at low temperatures. This has been described in particular in building paints which require application at room temperature and sometimes even below. On the other hand, coatings on wood, leather or industrial paints tolerate crosslinking at higher temperatures.

The crosslinkable systems at low or medium temperature are generally based on the combination of two elements which are the use of functional monomers copolymerized during the synthesis of the binder and the addition after the synthesis or at the time of implementation of a cross-linking multifunctional agent. As an indication, EP 552469, EP 555774 and EP 653469 describe the crosslinking of a functional latex based on acetoacetoxyethyl with a polyamine. On the other hand, EP 581466 crosslinks the same latex with a polyaldehyde. The major drawback of these systems is that the crosslinking agent is generally a small molecule added to the solution after the synthesis of the latex. This molecule, by its size and its partition coefficient between aqueous phase and organic phase (polymer) diffuses in the polymer, causing pre-crosslinking and making storage of the dispersion difficult, even impossible.

Certain articles and publications such as Polym. Mater. Sci. Ing. Eng. 56 pages 780 to 784; 1,987 and Polym. Mater. Sci. Ing. Eng. 59 pages 1 1 56 to 1 1 60; 1 988, mention the obtaining, under particular conditions (pH, catalysts, reagents, etc.) of films which can be crosslinked at room temperature from latex carrying an acetal function of the acrylamido butyraldehyde dialkyl acetal type, generally designated by ABDA. This crosslinking carried out in the presence of ammonium salts can only be obtained with this type of acetal because it is due to the ability of ABDA to lead to a cyclic form of the pendant chain, thus having sufficient reactivity. to crosslink.

The problem which the invention seeks to solve is to find an aqueous dispersion which is stable on storage and which leads, at the time of filming at low temperature, to a crosslinked film without the intervention of crosslinking agents. The Applicant has found that aqueous dispersions based on functionalized acetal polymers or aldehydes synthesized in an acid medium constitute an ingenious solution to the problem mentioned above.

Indeed, the Applicant has found that such dispersions containing or not acrylamide as co-monomer are stable on storage and lead during or after the coalescence at room temperature, whatever the degree of acidity (the pH) in use, and sometimes at a lower temperature at a crosslinked film having properties improved compared to an uncrosslinked film. The crosslinking can be activated by a heat treatment.

As crosslinking is carried out without the intervention of crosslinking agents, these systems are called, within the meaning of the invention, single-component systems.

The advantage of the composition of the invention is that the active function of the crosslinking is the aldehyde function. This is latent in the latex due to the presence of water, in the form of the hydrated aldehyde function and can only be generated during the evaporation of water. It can then react with itself or with acrylamide to lead to crosslinking at room temperature.

This aldehyde function can be obtained by copolymerization of an aldehyde monomer, of an acetal monomer in an acid medium or by acidification of a functionalized acetal latex synthesized in a neutral or basic medium.

Another advantage lies in the fact that the absence of a small reactive molecule capable of diffusing into the particles guarantees better storage stability.

One of the objects of the invention is an aqueous dispersion of particles of at least one polymer with a diameter of between 50 and 500 nm, said polymer consisting of: from 0.1 to 50% by weight of the residue of monomer A carrying a function acetal, aldehyde or masked acetal, of

50 to 99.9% by weight of residue of at least one monomer B copolymerizable with A.

The monomers A are chosen from group I containing

- aldehydes such as acrolein, methacrolein, formyl styrol, crotonaldehyde.

- aldehydes corresponding to the formula:

C H = C R, - C - E - G - C HO

II o - masked aldehydes corresponding to the following formulas

OR ₂ CHy- CR _f - C - E - G - CH ϋ

OCH ₂ = CH - CH R ₄ O formulas in which

- Rq represents hydrogen or methyl,

- R2 and R3, identical, each represent a C- alkyl group | - Cs, or else together form a group - CH ₂ -CR _S R ₆ - (CH ₂ ) ~ - where n = O or 1, R5 and Rg which are identical or different, each represent hydrogen or methyl,

- R4 represents a C2 - C4 alkylene,

- E represents O, NH or NR 'where R' represents a hydrogen or a C ₃ -C ₃ alkyl,

- G represents a C- alkylene residue | - C4 or a remainder

- CH

I

OR ₇ where R7 represents hydrogen or C-] - C4 alkyl. The preferred monomer A1 can be chosen from: - N- (2,2-dialkoxy 1-hydroxy ethyl) - (meth) acrylamides and

N- (1,2,2-trialkoxy ethyl) - (meth) acrylamides, the term alkoxy meaning C1-C4 alkoxy, such as

. N- (2,2-dimethoxy 1-hydroxy ethyl) -acrylamide (DMH); . N- (2,2-dimethoxy 1-hydroxy ethyl) -methacrylamide; . N- (1,2,2-trimethoxy ethD-acrylamide;

. N- (1,2,2-trimethoxy ethyl) -methacrylamide;

. N- (2,2-dibutoxy 1-hydroxy ethylD-acrylamide;

. N- (2,2-dibutoxy 1-hydroxy ethyl) -methacrylamide; . N- (1,2,2-tributoxy ethD-acrylamide;

. N- (1,2,2-tributoxy ethyl) -methacrylamide;

. N- (2,2-dimethoxyethyl) -methacrylamide;

- 2 vinyl 1, 3 dioxolane; - 4-acrylamidobutyraldehyde dimethyl or diethyl acetal (ABDA);

- methacrylamidoacetaldehyde dimethyl, or diethyl acetal (MAAMA);

- diethoxypropyl acrylate;

- diethoxypropyl methacrylate; 0 - acryloyloxopropyl-1, 3-dioxolane;

- methacryloyloxopropyl-1, 3-dioxolane; and

- N- (1,1-dimethoxy-but-4-y1) methacrylamide.

According to an advantageous form of the invention A1 is DMH or MAAMA. 5 The monomer B is chosen from group II containing:

- the acrylates and methacrylates corresponding to the following general formula:

in which _Q R ₈ - < ^CH 2> n, ^{with nl} "1 * * 4

R ₉ = H or C „ ₂ F _{2n 2} + l

- (meth) acrylic, itaconic or maleic acids

- (meth) acrylamide

- styrene and its derivatives 5 - vinyl acetate

- acrylonitrile

- ethylene

- vinyl chloride

- the esters of versatic acid corresponding to the formula: OR | 0

He I

CH = CH - O - C - C - R < ₂ I

in which

^R 10 ' ^R 1 1 ^{and R} 12 ^≈ H or C pC g alkyl

The acetal functionalized latexes can be obtained in accordance with the emulsion polymerization techniques known to a person skilled in the art by copolymerization of an acetal monomer (DMH,

MAAMA, ABDA, etc.), in the presence of other various comonomers and in particular acrylamide which improves the efficiency of crosslinking.

The acetal functionality can also be obtained by synthesis of a functionalized acrylamide latex or by synthesis of a latex comprising an acrylic monomer, then a posteriori modification of the latex respectively, by dimethoxy ethanal (DME) according to US 491 81 39, or by transesterification in the presence of a titanate type catalyst with the amino butyraldehyde di alkyl acetal (ABAA) according to J. of Applied Polymer Science vol. 51, 1063-1070, 1 994.

Another object of the invention is a process for obtaining crosslinked film at room temperature from the latexes of the invention.

This process consists in applying either latex as it is when it is prepared in an acid medium whatever the pH of the process, or acidified latex when it is prepared in basic or neutral medium followed by a drying at room temperature or below 40 ° C, without the intervention of crosslinking agents.

Indeed, the Applicant has found that the active function in terms of crosslinking is in fact aldehyde, which can be obtained by deprotection of the acetal function in an acid medium. However, in the presence of water, the aldehyde is in a hydrated (non-reactive) form which will only become active again during drying and therefore filmification.

For the implementation of the invention, the procedure is as follows: - an emulsion is polymerized in an acidic, neutral or basic medium, a mixture containing the monomers A and B in the proportions defined above,

^• the latex obtained is brought to the pH required by the application, generally at a pH between 2 and 10.

^• the latex is then applied to any support and dried at room temperature.

Each latex is then analyzed at the level of the properties of the film obtained by drying at room temperature, then of the same film after an additional heat treatment of 15 minutes at 160 ° C.

The properties of the film evaluated are the resistance to the solvent which is determined by measurements of the percentages of insolubles of test pieces immersed in acetone at room temperature for 24 h and the percentage of acetone absorbed by these same test pieces that we call index swelling, as well as the mechanical properties of the film through a tensile test (determination of the stress and elongation at break).

The degree of crosslinking of the film and therefore its good application properties will be characterized by the highest possible rate of insolubles, the lowest possible swelling index, as well as the highest possible stress and elongation at break.

The existence of crosslinking at room temperature of the film during coalescence will be demonstrated by comparing the properties before and after heat treatment. The following examples illustrate the invention without limiting its scope.

Example 1

Synthesis of DMH functionalized latexes in acidic medium

The latexes were synthesized in a conventional manner according to a semi-continuous polymerization process by simultaneous and separate addition of an initiator solution and a preemulsion on a base stock, previously heated to 75 ° C., located in the reactor, equipped with circulation of hot water in the double jacket, a central agitation, and a condenser.

Tank foot

Water 54.00 parts

REWOPAL NOS 25 0.25

REWOPAL HV 25 0.05

Pre-emulsion

Water 62.00

REWOPAL OUR 25 2.25

REWOPAL HV 25 0.45

Monomers 1 00.00 Initiator solution

Water 6.00

Sodium persulfate 0.30

The quantities are expressed in parts of active ingredients, the

REWOPAL NOS 25 being an ethoxylated sodium sulfate nonyl phenol marketed by the company WITCO at 35% in water, while the

REWOPAL HV 25 is an ethoxylated nonyl phenol marketed by the same company with 1,00% active material.

Procedure

Introduce the base stock into the reactor, homogenize and bring to 75 ° C. When the bottom temperature reaches 75 ° C, pour the pre-emulsion and the initiator solution in 4 hours. Leave to react for an additional hour at 75 ° C.

Cool to room temperature, and filter through a 100 micron canvas.

Characteristics of synthesized latex

The characteristics of the synthesized products are as follows:

The amounts of monomers are expressed in% by weight of active material, the Highlink DMH being sold in 50% aqueous solution by the company Hoechst (2% by weight of DMH corresponds to 1.2 mol%).

Example 2

Synthesis of DMH functionalized latexes in basic medium

The latexes were synthesized according to a similar process, certain syntheses having been carried out in a buffered medium, sodium bicarbonate having been, in this case, introduced into the preemulsion. Other syntheses were carried out in an ammoniacal medium, 20% ammonia having been added to the preemulsion to obtain a pH of 8, the pH in the reactor having thus been maintained above 6.

Tank foot

Water 54.00 parts

REWOPAL NOS 25 0.25

REWOPAL HV 25 0.05

Pre-emulsion

Water 62.00

REWOPAL OUR 25 2.25

REWOPAL HV 25 0.45

Monomers 100.00

NaHCO3 (0.20)

Ammonia 20% (qsq pH = 8)

Primer solution

Water 6.00

Sodium persulfate 0.5

Characteristics of synthesized latex

The characteristics of the synthesized products are as follows:

Dry extract 44.7 44.0 45.7 45.1 45.6 44.5

PH 6.3 6.2 6.3 8.0 8.0 8.0

Diameter (nm) 155 160 171 177 178 166

Viscosity (mPa.s) <100 <100 <100 <100 <100 <100 Example 3

Synthesis of DMH functionalized latexes via Acrylamide in basic medium

The latexes were first of all synthesized according to a process analogous to Example 1

Tank foot

Water 54.00 parts

REWOPAL NOS 25 0.25

REWOPAL HV 25 0.05

Pre-emulsion

Water 62.00

REWOPAL OUR 25 2.25

REWOPAL HV 25 0.45

Monomers 1 00.00

Primer solution

Water 6.00

Sodium persulfate 0.50

Characteristics of synthesized latex

The characteristics of the synthesized products are as follows:

0.85% by weight of acrylamide corresponds to 1.2 mol%. DME reaction on latex

After synthesis, the latexes are brought to pH 8 by adding ammonia and then at 45 ° C. with stirring. Dimethoxyethanal is then added in an amount less than or equal to the acrylamide stoichiometry, to lead to a DMH functionalized latex optionally having residual acrylamide functions. The reaction is maintained at 45 ° C for 7 hours with stirring. The latex is then cooled and characterized as above.

Characteristics of synthesized latex

The characteristics of the films finally obtained are as follows

DME is sold in a 60% aqueous solution by the company HOECHST, the amounts of Acrylamide and of final DMH being calculated by admitting a yield of the acrylamide + DME reaction of 100%.

Example 4

Synthesis of MAAMA functionalized latexes in acidic medium

Synthesis identical to that of Example 1

Reference 4.1 Methyl methacrylate 34%

Butyl acrylate 63.5%

MAAMA 2.5%

Dry extract 44.5%

PH 2.5

Size 224 nm

Viscosity <100 mPa .S

Example 5

Synthesis of MAAMA functionalized latexes in basic medium

The latexes were synthesized according to a process analogous to that of Example 2, certain syntheses having been carried out in a buffered medium, sodium bicarbonate having been, in this case, introduced into the preemulsion.

Tank foot

Water 54.00 parts

REWOPAL NOS 25 0.25

REWOPAL HV 25 0.05

Pre-emulsion

Water 62.00

REWOPAL OUR 25 2.25

REWOPAL HV 25 0.45

Monomers 100.00

NaHCO3 (0.30) Initiator solution

Water 6.00

Sodium persulfate 0.50

Characteristics of synthesized latex

The characteristics of the synthesized products are as follows:

Example 6

Study of the crosslinking of films from latex at different pH

The degree of pre-crosslinking of each latex film obtained by drying for 21 days at 23 ° C, 50% RH, and the degree of thermal post-crosslinking of the films dried as above and then subjected to a heat treatment for 1 5 min at 1 60 ° C, were determined by a measurement of insoluble levels and percentages of absorbed acetone (swelling index), on test pieces (average of 3 measurements), after 24 h immersion in acetone.

The dimensions of the test pieces are 10 x 25 mm, the thickness being between 1 and 2 mm.

Films were made directly from the latexes synthesized previously and then from the same latexes worn, depending on the case, at acidic pH (pH = 2) by adding 10% hydrochloric acid, or brought to basic pH (pH = 8) by adding 20% ammonia. Example 7

Mechanical properties of films from latex at different pH

The mechanical properties of the same films as above were determined through a tensile test carried out according to the ISO standard.

527.

Claims

1. An aqueous dispersion consisting of particles of at least one polymer with a diameter between 50 and 500 nm, said polymer containing from 0.1 to 50% by weight of monomer units carrying an acetal or aldehyde function, characterized in that said crosslink dispersion by film-forming at a temperature below 40 ° C in a neutral, acidic or basic medium.

2. Dispersion according to claim 1 as can be obtained by emulsion polymerization of a mixture of monomers containing:

- from 0.1 to 50% by weight of at least one monomer A carrying an acetal or aldehyde function, - from 50 to 99.9% by weight of at least one monomer B copolymerizable with A, said dispersion then being carried at the pH required by the application.

3. Dispersion according to claim 2 characterized in that the polymerization is carried out in an acid medium.

4. Dispersion according to claim 2 characterized in that the polymerization is carried out in neutral or basic medium followed by acidification.

5. Dispersion according to one of claims 2 to 4 characterized in that A is chosen from group I containing:

- aldehydes such as acrolein, methacrolein, formyl styrol, crotonaldehyde. - aldehydes corresponding to the formula: CH ₂ = C ₁ - C - E— G - CHO O

- masked aldehydes corresponding to the following formulas

OR>

CH ₉ - CR, E - G - CH r »OR.

O CH ₂ - CH - CH R ₄ O formulas in which

- R-] represents a hydrogen or a methyl,

- R2 and R3, identical, each represent a Cj - Cs alkyl group, or else together form a group CH ₂ - CR ₅ R ₆ - (CH ₂ ) _fi - where n = 0 or 1, R5 and Rg identical or different , each represent hydrogen or methyl,

- R4 represents a C2 - C4 alkylene, - E represents O, NH or NR 'or R' represents a hydrogen or a ^C 1 ^" C3 alkyl,

- G represents a C-] alkylene residue - C4 or a C H residue

I

OR ₇ where R7 represents a hydrogen or a C- \ - C4 alkyl.

6. Dispersion according to claim 5 characterized in that A is N- (2,2 dimethoxy 1-hydroxy ethyDacrylamide (DMH) or methacrylamidoacetaldehyde dimethyl acetal (MAAMA).

7. Dispersion according to one of claims 2 to 6 characterized in that the monomer B is chosen from group II containing

- the acrylates and methacrylates corresponding to the following general formula: CH ₂ = C - C - O - R ₈ - R ₉ O in which

R ₈ ≈ ( ^CH 2) n _< with ni = 1 to 14

R ₉ = H or C _n2 F ₂ „ ₂ + l - (meth) acrylic, itaconic or maleic acids

- (meth) acrylamide

- styrene and its derivatives

- vinyl acetate

- acrylonitrile - ethylene

- vinyl chloride

- the esters of versatic acid corresponding to the formula

O R.O

He I

CH ₂ = CH - O - C - C - R, ₂

Ru in which

^R 10 ' ^R ll ^{and R} 12 ⁼ H or Cj-Cg alkyl

8. Process for obtaining crosslinked film at ambient temperature from the dispersion of claim 1, consisting in that:

- the dispersion is brought to a pH of between 2 and 10 depending on the application,

- The dispersion is then applied to the support to be treated and dried at room temperature.

9. Application of the method of claim 8 to the surface treatment of materials such as glass, leather, paper, metal, wood, plastic building materials, adhesives, treatment of textiles.