Process for the preparation of a polysulfide

Abstract

Pre-polymer according to structure (I) X(R.sup.2O).sub.nCH.sub.2O(R.sup.1O).sub.mCH.sub.2(OR.sup.2).sub.pX (I) wherein R.sup.1 and R.sup.2 can be the same or different and are selected from alkane chains containing 2-10 carbon atoms, X is a halogen atom, and n, m, and p are integers that can be the same of different and have a value in the range 1-6. The use of this pre-polymer in the preparation of a liquid polysulfide polymer allows better control over the sulfur and oxygen content and the polarity of the resulting polymer.

Claims

1. Process for the preparation of a polysulfide comprising the step of reacting a bis(2-dihaloalkyl)formal and a dihaloalkane with sodium polysulfide in the presence of the pre-polymer according to structure (I)
X(R.sup.2O).sub.nCH.sub.2O(R.sup.1O).sub.mCH.sub.2(OR.sup.2).sub.pX(I) wherein R.sup.1 and R.sup.2 can be the same or different and are selected from alkane chains containing 2-10 carbon atoms, X is a halogen atom, and n, m, and p are integers that can be the same or different and have a value in the range 1-6.

2. Process according to claim 1 wherein the bis(2-dihaloalkyl)formal is bis(2-dichloroalkyl)formal.

3. Process according to claim 1 wherein the dihaloalkane is an alpha-omega dihaloalkane.

4. Process according to claim 1 wherein the dihaloalkane is a dichloroalkane.

5. Process according to claim 1 wherein the dichloroalkane is selected from the group consisting of 1,2-dichloroethane, 1,2-dichloropropane, 1,3-dichloropropoane, 1,4-dichlorobutane, 1,5-dichloro pentane, 1,6-dichloro hexane, and isomers and combinations thereof.

6. Process according to claim 1 wherein the product resulting from the reaction of the bis(2-dihaloalkyl)formal, the dihaloalkane, and sodium polysulfide in the presence of the pre-polymer is treated with a reducing agent in order to obtain a liquid polysulfide.

7. Process for the preparation of a polysulfide comprising the step of reacting a bis(2-dihaloalkyl)formal and a dihaloalkane with sodium polysulfide in the presence of a pre-polymer obtained by a process wherein a polyol is reacted with (para)formaldehyde and a halo-alcohol in the presence of an acid catalyst.

8. Process according to claim 7 wherein the polyol is selected from the group consisting of monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, monopropyele glycol, dipropylene glycol, tripropylene glycol, 1,4-butanediol, and mixtures thereof.

9. Process according to claim 7 wherein the halo-alcohol is a chloro-alcohol.

10. Process according to claim 9 wherein the chloro-alcohol is ethylene chlorohydrin.

Description

EXAMPLES

Example 1Synthesis of the Pre-Polymer

(1) A mixture of 4 moles paraformaldehyde, 7.5 moles ethylenchlorohydrin (ECH), 1 mole tetraethylene glycol (TEG) and 5.4 g HCl (added as 37% solution; calculated as pure HCl) per mole formaldehyde (calculated as CH.sub.2O) was heated with stirring to about 60 C. until the formaldehyde dissolved. The reaction mixture was then subjected to two azeotropic distillation steps under reduced pressure (head temperatures 120 mbar/54 C. and 20 mbar/94 C., respectively) in order to remove reaction water and excess ECH. The resulting product was a pre-polymer according to the present invention.

Comparative Example ASynthesis of a Polysulfide Polymer without Pre-Polymer

(2) A mixture of 2 moles paraformaldehyde (calculated as CH.sub.2O), 5 moles ethylenchlorohydrin (ECH) and 2.7 g HCl (added as 37% solution; calculated as pure HCl) per mole formaldehyde (calculated as CH.sub.2O) was heated with stirring to about 60 C. until the formaldehyde dissolved. The resulting reaction mixture was subjected to an azeotropic distillation under reduced pressure as described in Example 1 in order to remove reaction water and excess ECH. The resulting product was bis-(2-chloroethyl)formal (DF).

(3) 2.2 moles Na.sub.2S.sub.x (x=2.4), in an aqueous 2.1 mol/l solution, was treated with 25.1 g MgCl.sub.2, 12 g 50% NaOH solution (to form in situ Mg(OH).sub.2), and 10 mL of sodium butylnaphthalenesulfonate (a wetting agent) and heated to 88 C. A mixture of 1.32 moles DF, 0.88 moles dichloropropane (DCP) and 2 mole % (based on DF+DCP) of trichloropropane was added dropwise over 1 hour while keeping the temperature between 88 C. and 92 C. After addition of this mixture, the desulfurization agents (0.5 moles NaOH and 0.5 moles NaSH) were added and the reaction mixture was stirred for 2 hours at 100 C. After this time, the formed condensation latex was washed with water several times by decantation in order to remove any soluble salts.

(4) In a further step, the washed latex was treated with 0.18 moles (34 g 90%) sodium dithionite, 0.6 moles NaOH (48.9 g 50%) and 0.2 moles sodium bisulfite (50 mL 39.4% sol.) at 98 C. The reaction mixture was stirred for 30 minutes at this temperature. After that, the product was washed free of soluble salts and was coagulated by acidification with acetic acid to a pH in the range 4-5. After coagulation, the polymer was washed free of acetate ions and dewatered under reduced pressure (90 C., 20 mbar) resulting in a polymer with a number average molecular weight of 1800-2700 g/mol.

(5) This molecular weight was determined by Gel Permeation Chromatography (GPC) using polystyrene standards and by determination of the number of SH groups by way or titration with iodine, followed by back titration.

Example 2Synthesis of a Polysulfide Polymer With Pre-Polymer and DF

(6) Comparative Example A was repeated, except that 0.87 moles DF and 0.45 moles of the pre-polymer of Example 1 were used instead of the 1.32 moles of DF used in Comparative Example A.

(7) The resulting polymer had a molecular weight of 2000-3000 g/mol.

(8) The compatibility of the polysulfides according to Comparative Example A and Example 2 with different plasticizers was assessed by visual inspection of cured sealant matrices comprising the polysulfide and the plasticizer. If no migration of plasticizer out of the matrix was observed, the polysulfide and the plasticizer were considered compatible. If migration was observed, they were considered incompatible.

(9) In addition, the adhesion/cohesion behavior of the sealants to a glass substrate was evaluated in accordance with DIN 53504. Adhesion means: no chemical adhesion; only physical adhesion. Cohesion means: chemical adhesion.

(10) TABLE-US-00001 TABLE 1 Compatibility to plasticizer Plasticizer: Comp. Ex. A Ex. 2 3,3-oxydi-1-propanol dibenzoate Compatibitity to sealant formulation Compatible Compatible Adhesion behaviour to glass substrate Cohesive Cohesive Alkyl (C7-C9) Benzyl Phthalate Compatibitity to sealant formulation Compatible Compatible Adhesion behaviour to glass substrate Cohesive Cohesive Alkyl (C4) Benzyl Phthalate Compatibitity to sealant formulation Compatible Compatible Adhesion behaviour to glass substrate Cohesive Cohesive Di-alkyl (C9) Phthalate Compatibitity to sealant formulation Incompatible Compatible Adhesion behaviour to glass substrate Adhesive Cohesive Chlorinated paraffins (chlorine content 45-55 wt %) Compatibitity to sealant formulation Compatible Compatible Adhesion behaviour to glass substrate Cohesive Cohesive

(11) The adhesion behavior of the polysulfides according to Comparative Example A and Example 2 to polymeric and inorganic surfaces was assessed in accordance with DIN 53504. The results are listed in Table 2.

(12) TABLE-US-00002 TABLE 2 Adhesion to different surfaces Substrate: Comp. Ex. A Ex. 2 OH-terminiated Polybutadiene-based polyurethanes Modulus at 25% elonagtion [N/mm.sup.2] 0.51 0.59 Tensile strength [N/mm.sup.2] 1.36 1.52 Break-Type (Cohesive/Adhesive) Adhesive/ Cohesive Cohesive Polyurethanes (PUR) (Polyether-based) Modulus at 25% elonagtion [N/mm.sup.2] 0.45 0.59 Tensile strength [N/mm.sup.2] 1.53 1.62 Break-Type (Cohesive/Adhesive) Adhesive/ Cohesive Cohesive Polyacrylates (PMMA) Modulus at 25% elonagtion [N/mm.sup.2] 0.79 0.92 Tensile strength [N/mm.sup.2] 1.57 1.69 Break-Type (Cohesive/Adhesive) Cohesive Cohesive Polyester (PES) Modulus at 25% elonagtion [N/mm.sup.2] 0.72 0.84 Tensile strength [N/mm.sup.2] 1.54 1.74 Break-Type (Cohesive/Adhesive) Cohesive Cohesive Polysulfides (Bis (2-chlorethyl) formal based) Modulus at 25% elonagtion [N/mm.sup.2] 1.19 1.29 Tensile strength [N/mm.sup.2] 2.25 2.38 Break-Type (Cohesive/Adhesive) Cohesive Cohesive Epoxies (EP) Modulus at 25% elonagtion [N/mm.sup.2] 0.84 0.90 Tensile strength [N/mm.sup.2] 1.75 1.83 Break-Type (Cohesive/Adhesive) Cohesive Cohesive Stainless steel Modulus at 25% elonagtion [N/mm.sup.2] 1.05 1.09 Tensile strength [N/mm.sup.2] 1.79 1.87 Break-Type (Cohesive/Adhesive) Cohesive Cohesive Galvanized steel Modulus at 25% elonagtion [N/mm.sup.2] 0.99 1.14 Tensile strength [N/mm.sup.2] 1.73 1.94 Break-Type (Cohesive/Adhesive) Cohesive Cohesive Aluminium (anodized) Modulus at 25% elonagtion [N/mm.sup.2] 0.97 1.06 Tensile strength [N/mm.sup.2] 1.67 1.88 Break-Type (Cohesive/Adhesive) Cohesive Cohesive Glass Modulus at 25% elonagtion [N/mm.sup.2] 0.93 1.11 Tensile strength [N/mm.sup.2] 1.94 1.96 Break-Type (Cohesive/Adhesive) Cohesive Cohesive

(13) The chemical resistance of the two polysulfides towards different liquids was tested by measuring the swelling characteristics in accordance with DIN 53521. The results are listed in Table 3.

(14) TABLE-US-00003 TABLE 3 Swelling characteristics Liquid: Comp. Ex. A Ex. 2 Diesel after 7 days, 23 C. [%] 4.73 3.99 after 21 days, 23 C. [%] 7.85 6.89 Kerosine after 7 days, 23 C. [%] 4.53 3.79 after 21 days, 23 C. [%] 7.65 6.45 Petrol after 7 days, 23 C. [%] 4.41 3.75 after 21 days, 23 C. [%] 7.54 6.17 Toluene after 7 days, 23 C. [%] 4.01 3.65 after 21 days, 23 C. [%] 7.24 6.03 Ethanol after 7 days, 23 C. [%] 3.37 3.09 after 21 days, 23 C. [%] 5.92 5.70 Water after 7 days, 23 C. [%] 2.35 2.15 after 21 days, 23 C. [%] 4.92 4.73

(15) The above results show that the polysulfide prepared in accordance with the process of the present invention adheres better to a wide range of surfaces, is compatible with a wider range of plasticizers, and has a higher chemical resistance.