Polyurethane prepolymer with cyclocarbonate end groups of low viscosity and the use thereof in the production of a multi-component adhesive composition

Abstract

1) Specific polyurethane prepolymer (PP2) comprising at least two terminal (2-oxo-1,3-dioxolan-4-yl)methyl carbamate groups of low viscosity, its preparation process and its use in the manufacture of an adhesive composition. 2) Multicomponent system comprising, as first component (A), a composition comprising at least one such polyurethane prepolymer and, as second component (B), a composition comprising at least one curing agent having at least two primary amine (NH.sub.2) groups (B1). 3) Process for assembling materials employing the polyurethane prepolymer (PP2) according to the invention.

Claims

1. A process for the preparation of a polyurethane prepolymer having (2-oxo-1,3-dioxolan-4-yl)methyl carbamate end groups (PP2) comprising a stage of polyaddition reaction (denoted E2): of at least one compound (PP1) having at least two NCO groups and at least one divalent unit of formula (I): ##STR00016## in which: p is an integer ranging from 1 to 2; q is an integer ranging from 0 to 9; R represents a saturated or unsaturated, linear or branched, cyclic or acyclic, hydrocarbon chain of 1 to 20 carbon atoms; R.sup.3 represents a saturated, linear or branched, divalent hydrocarbon group of 2 to 4 carbon atoms; with at least one glycerol carbonate, at a reaction temperature T2 of less than 95 C., under anhydrous conditions, in amounts of compound (PP1) and of glycerol carbonate resulting in an NCO/OH molar ratio, denoted r2, ranging from 0.8 to 1.0.

2. The preparation process as claimed in claim 1, wherein the compound(s) (PP1) is (are) hexamethylene diisocyanate (HDI) allophanate compounds of formula (I): ##STR00017## in which: p is an integer ranging from 1 to 2; q is an integer ranging from 0 to 9; R represents a saturated or unsaturated, linear or branched, cyclic or acyclic, hydrocarbon chain of 1 to 20 carbon atoms; R.sup.3 represents a saturated, linear or branched, divalent hydrocarbon group having from 2 to 4 carbon atoms.

3. The preparation process as claimed in claim 1, wherein the compound(s) (PP1) is (are) polyurethane prepolymers having NCO end groups capable of being obtained by a polyaddition reaction: (i) of a diisocyanate composition comprising at least one hexamethylene diisocyanate (HDI) allophanate compound of formula (I), ##STR00018## in which: p is an integer ranging from 1 to 2; q is an integer ranging from 0 to 9; R represents a saturated or unsaturated, linear or branched, cyclic or acyclic, hydrocarbon chain of 1 to 20 carbon atoms; R.sup.3 represents a saturated, linear or branched, divalent hydrocarbon group having from 2 to 4 carbon atoms (ii) with at least one polyether polyol, at a reaction temperature T1 of less than 95 C., under anhydrous conditions and in amounts of diisocyanate(s) and of polyether polyol(s) resulting in an NCO/OH molar ratio, denoted r1, ranging from 1.6 to 1.9.

4. The preparation process as claimed in claim 3, wherein the polyether polyol(s) is (are) polyoxyalkylene polyols, a linear or branched alkylene part of which has 1 to 4 carbon atoms and the average molar mass of which ranges from 200 to 20 000 g/mol.

5. The preparation process as claimed in claim 1, that does not comprise adding one or more solvent(s) and/or plasticizer(s).

6. A polyurethane prepolymer having (2-oxo-1,3-dioxolan-4-yl)methyl carbamate end groups (PP2), capable of being obtained by the preparation process as defined in claim 1.

7. A multicomponent system, comprising: as first component (denoted component (A)), a composition comprising at least one polyurethane prepolymer having (2-oxo-1,3-dioxolan-4-yl)methyl carbamate end groups (PP2), as defined in claim 6, and as second component (denoted component (B)), a composition comprising at least one curing agent having at least two primary amine (NH.sub.2) groups (B1).

8. The multicomponent system as claimed in claim 7, wherein the primary amine groups of said curing agent(s) (B1) are methylene(primary amine) (CH.sub.2NH.sub.2) groups.

9. The multicomponent system as claimed in claim 7, wherein the amounts of polyurethane prepolymer(s) having (2-oxo-1,3-dioxolan-4-yl)methyl carbamate end groups (PP2) and of curing agent(s) having at least two primary amine groups (B1) as defined in claim 7 present in the multicomponent system result in a molar ratio of the number of cyclocarbonate groups to the number of primary amine groups, denoted r3, ranging from 0.5 to 1.

10. The multicomponent system as claimed in claim 7, comprising at least one inorganic filler.

11. A process for assembling materials employing the polyurethane prepolymer having (2-oxo-1,3-dioxolan-4-yl)methyl carbamate end groups (PP2) as defined in claim 6, comprising: mixing of at least one polyurethane prepolymer having (2-oxo-1,3-dioxolan-4-yl)methyl carbamate end groups (PP2) and of at least one curing agent having at least two primary amine (NH.sub.2) groups (B1), then coating of said mixture onto the surface of a first material, then laminating of the surface of a second material onto said coated surface, then crosslinking of said mixture.

12. In an adhesive composition comprising a polyurethane polymer, the improvement wherein the polymer is produced from a polyurethane prepolymer having (2-oxo-1,3-dioxolan-4-yl)methyl carbamate end groups (PP2) as defined in claim 6.

Description

EXAMPLES 1 AND 2: SYNTHESIS OF THE POLYURETHANE PREPOLYMER HAVING CYCLOCARBONATE END GROUPS (PP2) (COMPONENT A) IN ONE STAGE (E2)

(1) The diisocyanate is heated to 50 C. in a reactor placed under a nitrogen atmosphere and then the glycerol carbonate is introduced in the proportions shown in table 1. The mixture is subsequently brought to 80 C. and the catalyst is added. This mixture is kept continuously stirred at 80 C., under nitrogen, until complete disappearance of the NCO functional groups visible in the infrared (IR) (approximately 2250 cm.sup.1).

(2) 100 g of prepolymer (PP2) (component A) are obtained at the end of the reaction for each of the examples.

EXAMPLE 3: SYNTHESIS OF THE POLYURETHANE PREPOLYMER HAVING CYCLOCARBONATE END GROUPS (PP2) (COMPONENT A) IN TWO STAGES (E1 AND E2)

Stage E1: Synthesis of the Compound (PP1)

(3) The diisocyanate is heated to 50 C. in a reactor placed under a nitrogen atmosphere and then a mixture of polyether polyol and of reaction catalyst, in accordance with the amounts shown in table 1, is introduced dropwise with continuous stirring. The temperature does not exceed 80 C.

(4) This mixture is kept continuously stirred at 80 C., under nitrogen, until the NCO functional groups of the diisocyanate have completely reacted.

(5) The reaction is monitored by measuring the change in the content of NCO groups in the mixture, for example by back titration of dibutylamine using hydrochloric acid, according to the standard NF T52-132. The reaction is halted when the degree of NCO (% NCO) measured is approximately equal to the desired degree of NCO (2.2% by weight of the weight of the reaction mixture).

Stage E2: Synthesis of the Polyurethane Prepolymer Having Cyclocarbonate End Groups (PP2) (Component A)

(6) Once the reaction of stage E1 is complete, the glycerol carbonate is introduced into the reactor in the proportion shown in table 1, with stirring and under nitrogen. The temperature does not exceed 80 C.

(7) The compound (PP1)/glycerol carbonate mixture is kept continuously stirred at 80 C. under nitrogen until complete disappearance of the NCO functional groups visible in the infrared (IR) (approximately 2250 cm.sup.1).

(8) 100 g of prepolymer (PP2) (component A) are obtained at the end of the reaction.

(9) Viscosity Measurement:

(10) The viscosity of the component (A) obtained is measured 24 hours after the end of the reaction (D+1) at 23 C. and 60 C. and is expressed in pascal.Math.seconds (Pa.Math.s). All of the values measured for examples 1 to 3 are combined in the following table 2.

(11) The viscosity measurement at 23 C. is carried out using a Brookfield RVT viscometer, with a spindle suited to the viscosity range and at a rotational speed of 20 revolutions per minute (rev/min).

(12) The viscosity measurement at 60 C. is carried out using a Brookfield RVT viscometer coupled with a heating module of Thermosel type of the Brookfield brand, with a spindle suited to the viscosity range and at a rotational speed of 20 revolutions per minute.

(13) TABLE-US-00002 TABLE 2 Characterization of the polyurethane prepolymer having cyclocarbonate end groups (PP2) 1 2 3 Viscosity at D + 1 at 23 C. (Pa .Math. s) 300 300 110 Viscosity at D + 1 at 60 C. (Pa .Math. s) 3.6 3.6 6.7 Calculated content of cyclocarbonate 2.40 2.48 0.57 groups in the prepolymer (PP2) (meq/g of prepolymer (PP2)), denoted t.sub.cc (PP2)

(14) The content of cyclocarbonate groups in the prepolymer (PP2) (denoted t.sub.cc (PP2)) (expressed in meq/g of prepolymer (PP2)) is calculated in a way well known to a person skilled in the art from the molar amount of glycerol carbonate used. By expressing the number of mole(s) of glycerol carbonate used as a function of the hydroxyl number (mg KOH/g) of the latter and of the molar mass of KOH equal to 56 g/mol, it is possible to write:

(15) $t_{\mathrm{cc}}\left(\mathrm{PP}2\right)=\frac{\mathrm{OHN}\left(\mathrm{glyercol}\mathrm{carbonate}\right)w3\left(\mathrm{glycerol}\mathrm{carbonate}\right)}{56w\left(\mathrm{PP}2\right)}$
where:
OHN (glycerol carbonate) corresponds to the hydroxyl number of the Jeffsol GC,
w3 (glycerol carbonate) corresponds to the weight of Jeffsol GC introduced,
w (PP2) corresponds to the weight of prepolymer (PP2), i.e. to the total weight of the ingredients used for the synthesis of the prepolymer PP2 (derivative of formula (I), PPG diol, reaction catalyst).

(16) BPreparation of the Compositions According to the Invention by Mixing the Components A and B

(17) The adhesive compositions 1 to 12 according to the invention are prepared by mixing the different ingredients shown in the following table 3, at a temperature T3 as shown below, under a nitrogen atmosphere. The mixture is kept continuously stirred under vacuum (for debubbling) for 2 minutes. The mixture is then left stirring until complete disappearance of the cyclocarbonate functional groups visible in the infrared (signal at 1800 cm.sup.1).

(18) The amounts shown in table 3 are expressed in grams.

(19) TABLE-US-00003 TABLE 3 1 2 3 4 5 6 7 8 9 10 11 12 Component A 100 100 100 100 100 100 100 100 100 of example 1 Component A 100 100 of example 2 Component A 100 of example 3 TAEA 12.2 12.2 12.2 12.2 12.2 12.2 6 6 6 2.85 HMDA 12 PEI 35.2 35.2 Dimeric fatty 35 35 amine Calcium 50 100 100 100 100 100 50 100 carbonate Molar ratio r3 0.96 0.96 0.96 0.96 0.96 0.96 0.96 0.73 0.96 0.93 0.93 0.97 Temperature 23 80 80 80 80 80 80 80 80 80 80 80 T3 ( C.)

(20) The following are used in table 3: tris(2-aminoethyl)amine (TAEA) with a primary alkalinity=20.52 meq/g of TAEA, hexamethylenediamine (HMDA) with a primary alkalinity=17.21 meq/g of HMDA, polyethyleneimine (PEI), sold under the name E100 by Huntsman, with a primary alkalinity=7.58 meq/g of PEI, dimeric fatty amine, sold under the name Priamine 1071 by Croda, with a primary alkalinity=3.65 meq/g of Priamine, calcium carbonate with a maximum particle size=100 m.

(21) The molar ratio r3 is calculated in a way well known to a person skilled in the art from the molar amounts of glycerol carbonate and of curing agent(s) having at least two primary amine (NH.sub.2) groups. By expressing the number of mole(s) of glycerol carbonate as a function of the content of cyclocarbonate groups in the prepolymer (PP2) calculated above and the number of mole(s) of aminated curing agent(s) used as a function of the primary alkalinity (meq/g) of the latter, it is possible to write:

(22) $r3=\frac{t_{\mathrm{cc}}\left(\mathrm{PP}2\right)w\left(\mathrm{PP}2\right)}{\underset{k}{.Math.}\left[w_k\left(\mathrm{aminated}\mathrm{curing}\mathrm{agent}\right){\mathrm{PA}}_k\left(\mathrm{aminated}\mathrm{curing}\mathrm{agent}\right)\right]}$
where:
t.sub.cc is the calculated content of cyclocarbonate groups in the prepolymer (PP2) (meq/g) as defined above,
w (PP2) corresponds to the weight of prepolymer (PP2) as defined above,
PA.sub.k is the primary alkalinity of each aminated curing agent,
w.sub.k (aminated curing agent) corresponds to the weight of each aminated curing agent k with alkalinity PA.sub.k used,
.sub.k[w.sub.k (aminated curing agent)PA.sub.k (aminated curing agent)] corresponds, for k=1, to the product of the weight of the aminated curing agent used and the primary alkalinity of said aminated curing agent and, for k>1, to the sum of the products of the weight of each aminated curing agent used and their respective primary alkalinity.
k is an integer greater than or equal to 1.

(23) Measurement of the Mechanical Performances: Breaking Strength and Elongation at Break of the Compositions According to the Invention in the Crosslinked State.

(24) Once crosslinked, the breaking strength and the elongation at break are measured by a tensile test on the adhesive composition according to the protocol described below.

(25) The principle of the measurement consists in drawing, in a tensile testing device, the movable jaw of which is displaced at a constant rate equal to 100 mm/minute, a standard test specimen consisting of the crosslinked adhesive composition and in recording, at the moment when the test specimen breaks, the applied tensile stress (in MPa) and also the elongation of the test specimen (as %).

(26) The standard test specimen has the shape of a dumbbell, as illustrated in the international standard ISO 37. The narrow part of the dumbbell used has a length of 20 mm, a width of 4 mm and a thickness of 500 m.

(27) In order to prepare the dumbbell, the conditioned composition as described above is heated to 95 C. and then the amount necessary to form, on an A4 sheet of silicone-treated paper, a film having a thickness of 500 m is extruded over this sheet, which film is left at 23 C. and 50% relative humidity for 7 days for crosslinking. The dumbbell is then obtained by simple cutting from the crosslinked film using a hollow punch.

(28) The tensile strength test is repeated twice and gives the same results. The applied tensile stress recorded is expressed in megapascals (MPa, i.e. 10.sup.6 Pa) and the elongation at break is expressed as % with respect to the initial length of the test specimen. The values are combined in table 4 below.

(29) TABLE-US-00004 TABLE 4 1 2 3 4 5 6 7 8 9 10 11 12 Applied 2.4 4.6 5.5 6.9 3.4 4.1 4 1.6 1.4 3.2 4.5 4.9 tensile stress (MPa) Elongation at 360 533 270 200 200 280 600 750 410 435 615 1230 break (%)

(30) Adhesiveness: Measurement of the Force of Shearing Under Stress (Lap Shear)

(31) Compositions 1, 2 and 8 according to the invention were furthermore subjected to tests of adhesive bonding of two small plates made of powdered aluminum (each with a size of 100 mm25 mm) cleaned beforehand with a solvent (isopropanol). The adhesive composition is applied to one of the surfaces of the small plates using a spatula, within a space delimited by a Teflon window of 12.5 mm25 mm. The other small plate is affixed over the adhesive-coated surface by pressing the two small plates against one another. After crosslinking at 23 C. and 50% relative humidity for seven days, the shear force at failure and also the failure facies are measured.

(32) TABLE-US-00005 TABLE 5 1 2 8 Shear force at failure (MPa) 2.3 4 0.6 Type of failure AF AF AF

(33) AF denotes adhesive failure, meaning that it is observed that all of the adhesive seal has remained adhesively bonded to one of the faces of the laminated small plates.

(34) Thus, the adhesive compositions according to the invention can be easily formulated using a preparation process which is relatively inexpensive in energy, which is friendly to man and to his environment and which does not employ solvent or plasticizer.

(35) In addition, the adhesive compositions according to the invention thus obtained result in adhesives which are effective in terms of mechanical properties and/or of adhesive force and which are suitable for a broad panel of applications.