DE2429782C3 - Process for foam stabilization in the production of polyisocyanate-modified polychloroprene foam - Google Patents

Description

RN (CH ₂ CHROH).,

where R is methyl or ethyl and R 'is hydrogen or methyl, added and the latex on one Adjusts the pH value from 10.0 to 11.5. > o

The invention relates to a method for show instabilization in the production of polychloroprene foams reinforced with polyisocyanates.

According to US Pat. No. 3,450,649, the incorporation of 10 to 100 parts of an organic polyisocyanate leads to 100 parts Parts elastomer into a latex of a sulfur curable one Elastomers and then expanding the latex into a foam to make foams that compared with Foams made from latexes that do not contain polyisocyanate have a low density and have improved load-bearing properties. Polychloroprene foams made in this way also have good flame resistance.

US Pat. No. 3,639,301, which goes back to the same inventor, describes an improved production of polyisocyanal-modified polychloroprene foam by heating freshly prepared polychloroprene latex with a pH of over II at 60 to 90 ^° C. until the pH has reached 9.5 to 10.0 is lowered. It is also known to lower the pH of polychloroprene latices by aging the latices for several weeks or months at room temperature.

According to the method of US Pat. No. 3,627,710, the pH of polychloroprene latices is lowered to 9.5 to 10.8, while polyisocyanate-modified foams produced from such latices are retained. The process requires the addition of a strong acid salt with certain secondary amines such as morpholine, diethanolamine, di- (2-propanol) amine, etc., to the latex. The latex, which contains about 50% residues, is creamed before or after pH adjustment, with the creamed latex containing about 58 to 60% solids. US Pat. No. 3,627,710 is based on the same task, the salt of a strong acid with certain secondary alkanol amines, for example with diethanolamine, being used to lower the pH. Table II shows a comparison between the properties of a foam obtained with a polychloroprene latex adjusted according to the invention (mass <■ <$ according to Example 1), compared to a control experiment in which, according to the prior art from US Pat 27 710 had been worked, namely using diethanolamine. The values in Table II clearly show the superiority of foams which have been produced with a polychloroprene latex treated according to the invention. Particularly noteworthy are the elongation, which is more than twice as high, and the significantly lower permanent deformation under pressure. Volume shrinkage and tensile strength are also considerably improved. It was therefore surprising to now use N-alkyl-substituted alkanolamines instead of dialkanolamine.

High solids latices are also obtained by polymerizing concentrated chlorobutylene emulsions can be produced directly by the process of US Pat. No. 3,651,038 and 3,651,037. Such by direct polymerization obtained latices of high solids content (hereinafter also referred to as "DPHS" latices for short however, speak to the pH adjustment processes of the state of the art does not apply; the resulting foams have an undesirably low level of hardening Resilience and, in the wet, unhardened state, poor resistance to permanent deformation vacuum. However, the property of permanent wet deformation under pressure must be good in order to Avoid deformation of the foam in the demolding stage before hardening.

There is, therefore, a strong need for an efficient process for the production of polyisocyanate fortified products Polychloroprene foam poles made from DPHS latices.

The present invention is a process for foam stabilization in the manufacture of polyisocyanate-modified products Polychloroprene latex foam with a latex pH greater than about 11.5 to about 10.0 to 11.5 by adding one Alkanol amine is set, which is characterized in that the polychloroprene latex with, in each case based on 100 parts by weight of latex solids, 0.5 to 3 parts by weight of a conventional, nonionic, surface-active agent with an HLB value of about 11 to 16.5 and 0.5 to 2.0 parts of an alkanol amine of the formula

RN (CH ₂ CHROH) ₂

(I!

where R is methyl or ethyl and R 'is hydrogen or methyl, added and the latex to a pH value sets from 10.0 to 11.5.

The addition of an amine of formula 1 to the latex and the pH adjustment can be carried out in a single step be united.

Latices for use in the method according to the invention can be conventional latices, such as those in US Pat. No. 3,627,710 or "DPHS" latices, such as those according to US Pat. No. 36,51038 and 36 51037. The pH of a freshly prepared, conventional latex is about 11 to 13 and that of a "DPHS" latex will be at least 10.5, preferably about 13. Polychloroprene latexes obtained by familiar methods by emulsifying chloroprene in water and in the presence polymerized by a catalyst. The foaming is achieved by "whipping" the emulsion with Brinjn air mechanically for foam formation and a gelling agent such as potassium silicofluoride is added. A conventional latex has a solids content of about 59% after creaming. The solids content of a "DPHS" latex is around 62%. While conventional

.1 °

The latices are usually mercaptan or sulfur-modified "DPHS" latices often contain xanthate modification before. The method according to the invention is particularly suitable for "DPHS" latices.

The polyisocyanate is preferably used at about the same time as the gelling agent or shortly before; adding the isocyanate much earlier can cause premature coagulation and result in a foam product with poor load-bearing properties. The polyisocyanates include aromatic diisocyanates such as 2,4- and 2,6-toluene diisocyanate, 4,4'-methylene-bis (phenyl isocyanate), m-phenylene diisocyanate, polymethylene poly (phenyl isocyanate) and toluene diisocyanate distillation residues with an isocyanate -Functionality of over 2. Aliphatic diisocyanates, such as 4,4'-methylene-bis-icyclohexyl isocyanate) and decamethylene diisocyanate are also suitable for the purposes of the invention, but are less good. A polymethylene poly (phenyl isocyanate), substantially as described in US-PS 26 83 730 was prepared and about 50 wt .-% of 4,4'-methylene-bis- contains (phenyl isocyanate) is particularly suitable. About 10 to 100 parts by weight of polyisocyanate are used for 100 parts by weight of elastomer in the latex.

On N-alkyl-substituted alkanolamines of the formula I for the purposes of the invention include methyldiethanolamine, ethyldiethanolamine, di- (2-hydroxypropyl) -methyljmin and di (2-hydroxypropyl) ethylamine. Methyl diethanolamine and ethyl diethanolamine will be preferred. A smaller amount of such a secondary amine as diethanolamine can also be used. exist; this additional amine is sometimes desirable because in one case or another it is the Gel quality increased.

Nonionic surfactants for purposes of the invention include condensation products of alkylphenols, fatty alcohols, vegetable oils, carboxylic acids or carboxamides with ethylene oxide. Suitable surfactants have an HLB value of about II to 16.5 on the basis of a Scale from 0 to 20. The HLB scale is the in the art surfactants familiar; a completely lipophilic material that has no hydrophilic properties has a value of 0 and a completely hydrophilic material is assigned a value of 20. Die The method for calculating the HLB value is in the "Journal of the Society of Cosmetic Chemists", Vol. I, p. 311 (1949). The addition of the nonionic surface-active agent takes place before the foam formation .so manure. The presence of a nonionic surfactant is essential for the method according to FIG Invention critical; in its absence, the foams produced produce the desired, good ones Properties not one.

In addition to the nonionic surfactant, an anionic surfactant can be used in the latex The agent is present in an amount from 0 to about 1 part per 100 parts latex solids, with this surfactant must derive the anion from a strong organic acid, e.g. B. sulfonate or sulfate. A typical well-suited anionic surfactant is a mixture of Sodium salts of sulfate monoesters of higher fatty alcohols, mainly laury and myristyl derivatives, The anionic surfactant is recommended for use in making Low density chloroprene foams. Be to-

5 p

(10 salt takes place before foam formation.

The amine of formula I and the nonionic surfactant are added to the latex before or after foam formation, but before the addition of polyisocyanate added. The amine and nonionic surfactant can be added separately or mix first and then add in a single step.

The pH adjustment can be effected in any convenient manner by getting into the latex introduces any suitable acid. It can be weak or strong organic or inorganic Acids find uses, including chemical compounds that form an acid in situ / .. B. Carbon dioxide. The acid or acid-forming compound can after the amine of the formula I or be added at the same time as this. Since a simultaneous addition /. at the beginning to the formation of the corresponding amine sulfate would lead, one can also use salts of the amines of the formula I instead of the free amines of formula I and acids work. Both variants of this working method are within the scope of Invention. If the amine of the formula I and a strong acid are added separately, the acid should be added in add enough diluted form to avoid coagulation of the latex. But one can do this undesirable dilution of the latex. It is therefore preferable to use a strong acid in the mixture with an amine of the formula I. The salt that forms can be added in much higher concentrations without causing coagulation, and dilution is minimal.

Acids for the purposes of the invention include, inter alia, hydrogen chloride, sulfur, nitric, Phosphoric, benzenesulphonic, hydrogen fluoride, hydrogen iodide, trifluoroacetic and trichloroacetic acid c. hydrochloric acid is the preferred acid because of its low cost and ready availability. Accordingly are Methyldiälhanolaniinhydrochlorid and Äthyldiäthanolaminhydrochlorid the preferred amine salts of formula 1, which can be used for one-step pH adjustment.

Foams produced by the process according to the invention are particularly suitable for the Use for cushions, carpets, upholstery, mattresses and other uses for whom good resilience and high load-bearing capacity are important. These desirable properties can be paired with low foam density; such low density foams have a exceptionally good suitability for use on ships and the like.

The following examples, in which parts, proportions and percentages refer to the Referring to weight, serve to further explain the invention on the basis of certain preferred embodiments.

First of all, the procedure used in the examples for foam production will be described.

The base mass was made by adding the ingredients listed in Table 1 in the order in which it was added formed with good agitation to polychloroprene latex. All ingredients up to and including petrolatum were generally premixed and added to the latex as a mixture along with the water added, which is used to adjust the total substance content, excluding polyisocyanate and gelling agent, was used to 60.5%. The water soluble

Materials, d. H. a common surfactant, nonionic surfactant, rubber accelerator, Diethanolamine. a common soap emulsifier made from modified resin acids and amines Formula I were then added as aqueous solutions so that a colloidal shock effect on the Latex was eliminated. The water-insoluble materials (with the exception of hydrated alumina) were added as colloidal emulsions or dispersions. The Ν, Ν-dimethyl-N'-ethylthiourea was used as a 55% dispersion. The dispersions of paraffins and microcrystalline waxes in Water was purchased from Mobil Oil Co. as a 50% dispersion. The thiocarbanilide, antimony oxide and a basic batch of phenyl-j? -naphthylamine and zinc oxide were ball-milled dispersions which according to recipes according to J.C. Carl, "Neoprene Latex", 1962 (E. I. du Pont de Nemours and Co., Inc.) were prepared. The hydrated alumina was added as a dry powder.

To produce the foam, the base material was mixed on a Hobart model 100-C mixer, the working at low, medium and high mixing speeds, with air in a foaming state offset, with both 2V4-1 and 9 '/ 2-1 containers with impact organs of appropriate size were used The desired volume took place at the high working speed, whereupon the foaming material took 6 min medium speed was refined. The polymethylene polyphenyl isocyanate was added at low speed and 1 minute at medium speed Speed mixed in. The sodium silicofluoride was then added at low speed

Table I.

and 1 min. at medium speed cingcmischL The foaming material was then poured into an open mold and the surface with a spatula smoothed.

Most foams are made at room temperature (21 to 24 ° C), but you can also use higher and lower temperatures work. The gel time decreases with increasing temperature, and, as given to those skilled in the art, is used to set the

ίο the gel time to a practice-oriented area Adjust the amount of gelling agent. The gel time is equal to the time between the addition of the Sodium Silicofluorides and the time at which the foaming material has completely gelled.

The latex used in Examples 1 and 2 was prepared essentially according to the procedure of Example 2 of US-PS 36 51 037 produced, the following changes were made (all parts per 100 parts Chloroprene): use of 0.10 part of diethylxanthogen disulfide instead of 0.1 part of dodecyl mercaptan; Use of 57 (instead of 60) parts of water; Use of 0.91 (instead of 1.5) parts of the potassium salt of Condensates of formaldehyde and alkylnaphthalenesulfonic acid; Submission of 0.1 part dextrose and 0.1 part Potassium sulfite in the chloroprene emulsion.

When the polymerization was complete, the latex was by adding 0.02 parts of phenothiazine and 0.022 Parts of 4-tert-butyl catechol as a solution in toluene, emulsified in water, stabilized.

In Example 3, the same latex was used and additionally worked with a content of 1.5 parts of a conventional soap emulsifier as post-additive.

Base ¹ ) Solids content, including additives, 60.5%. example
1 - 2.0 - 2.0 neutralized ² ) A common modified resin acid soap emulsifier 2 - 1.5 - 1.5 - 2.0 1.7 3 - 1.0 - 0.47 Polychloroprene 100.0 0.42 2.0 ¹¹ J Covers all methyl diethanolamine (be it as free amine or 100.0 0.32 2.0 100.0 - 0.25 Sodium lauryl sulfate ³ ) 1.0 7.5 1 0.6 7.5 1.0 0.25 Non-ionic agent ⁴ ) 1.5 5.0 5.0 Resin acids as post-additive. 2.0 Potassium Salt of Processed Rosin ¹² ) 1.5 16.0 20.0 7.5 Thiocarbanilide - - 5.0 N, N-dimethyl-N'-ethylthiourea - 20.0 Sodium dibutyldithiocarbamate ') Importance: to pH 11.0 Diethanolamine 1.75 Petrolatum ⁶ ) Contains 1.5 parts of a customary soap emulsifier made from modified Phenyl - /? - naphthylamine ⁷ ) Common surfactant. zinc oxide Alkylaryl polyether alcohol. Antimony oxide ⁸ ) added as hydrochloride). Hydrate. Aluminum oxide ⁹ ) with a solids content of 88%. Methyl diethanolamine hydrochloride ¹⁰ ) ⁵ l sodium dibutylthiocarbamal as a rubber accelerator (47%). Methyl diethanolamine, total ") ^b ) Usual wax emulsions. The reference numbers used in Table I have the following ') Phenyl / I-naphthylamine as a rubber antioxidant. 1 A Commercially available variety. 2 ⁹ J Hydrated Alumina. j ¹⁰ ΐ 2-molar solution of methyl diethanolamine, with HCI 80% 4th

I-ortsct / unc

Base ¹ )

example

Additive (see Tables II to IV)
Polymethylene polyphenyl isocyanate ¹³ )
Sodium silicofluoride (gelling agent)

') Solids content, including additives, 60.5%.
13) Commercially available variety.

to pH 11.0 to pH 11.0 - look there look there look there 20th 15th 17.5 2.5-3.4 3 3.5

25%, kg / cm *

Permanent deformation
vacuum, %

') Tested 45 minutes after gelation.

The wet foams were demolded 45 minutes after filling, and the wet recovery properties were determined immediately. The wet foam was quickly hand-washed to about 25% of its time The height is compressed and the pressure is immediately relieved. The recovery was rated as good, though the foam recovered fully, acceptable when the recovery was almost complete, but in the Surface slight indentations remained, and bad, if a substantial amount remained There was deformation under pressure.

The wet foams were dried and cured in a hot air circulation oven for 8 hours at 121 ^° C., after which the dimensions of the cured foam were determined and the volume shrinkage was calculated as a percentage of the mold volume. The density was calculated from the weight of a test specimen measuring 5.1 × 5.1 × 2.54 cm. The physical properties of the foam were determined in accordance with ASTM test standard D-1564-71.

The following Tables II to IV list the results relating to gel time, wet recovery and properties of the cured foam for Examples 1 through 3. In Table II is the additive Methyl diethanolamine according to the invention compared with the diethanolamine according to US Pat. No. 3,627,710. In in Tables III and IV, the effects of nonionic surfactants are several HLB values compared to one another. Table IV also gives values for the event that none nonionic surfactant is present

Table III

Mass according to example 2

Additive / H LB value / ÄO '),

Parts / 100 parts:

Common alkylaryl polyether alcohol 1,2

Common alkylaryl polyether alcohol 1,2

Common alkylaryl polyether alcohol 1,2

Common alkylaryl polyether alcohol

Common alkylaryl polyether alcohol

Comparative test gel time, min.

Foam properties:

Density, g / cm ³

Tensile strength, kg / cm ²

Strain, %

Flexure under pressure, 25%, kg / cm ²

Permanent deformation under pressure,%

') Average number of ethylene oxide units per mole of octylphenol

*) Only for comparison: outside of the present invention, because HLB value 173.

Table II 20th Additive, parts / 100 parts: 1.13 Control Mass according to example 1 Methyl diethanolamine attempt 25 diethanolamine 3.6 Gel time, min. Well Wet recreation ¹ ) 1.0 Foam properties: 0.083 2.1 _3O density, g / cm ³ 38 Well Volume shrinkage,% 0.84 Tensile strength, kg / cm ² 150 0.078 Elongation, ° / o 0.037 31 Bending under pressure 0.34 60 0.052

11th

22nd

These results show that you can have a good wet recovery in the presence of methyl diethanolamine as is also obtained in the presence of diethanolamine, abei in the cured foam according to the invention in the presence of Methyldiäthanolamir was produced, achieved a considerably higher tensile strength and elongation at break.

3.9 33 3.9 U ") 4.4 0.090 0.090 0.087 4.6 0.088 0.67 0.62 0.60 0.082 0.72 145 140 140 0.40 150 0.028 0.029 0.031 70 0.027 5.1 7.6 6.9 0.032 4.7 8.1

As these values show, in the presence of nonionic surfactants, their HLB values are in the range described, foams with excellent physical

Table IV

Mass according to example 3

Additive / H LB value / ÄO>),

Parts / 100 parts:

Common alkylaryl polyether alcohol Common alkylaryl polyether alcohol Gelling time, min.
Wet recreation ³ }

Properties. If the HLB value is the critical Exceeds the value, a foam with low tensile strength and low elongation at break is obtained.

2.9

excellent

Foam properties:

Density, g / cm ³ 0.066

Volume shrinkage,% 37

Tensile strength, kg / cm ² 0.34

Elongation,% 100

Flexure under pressure, 25%, kg / cm ² 0.021

Permanent set under pressure,% 13.3

■) Average number of ethylene oxide units / mole of octylphenol. Alkylaryl polyether alcohol.
Tested 45 minutes after gelation.

0.50

2.8

excellent

0.072

38

0.60

140

0.032

10.4 1.0

2.8

excellent

0.072

39

0.72

160

0.032

8.3

1.5

3.3

excellent

0.074

0.89

180

0.028

9.4

2.0

3.6

excellent

0.074

40

0.82

170

0.028

9.7

1.5 3.7

excellent

0.078

43

0.87

170

0.035

8.2

These results show that foams can be produced in the presence of a nonionic surfactant with excellent properties obtained in the absence of a surfactant drops Foam with very low tensile strength and only moderate elongation at break.

Claims (1)

Claim: Process for foam stabilization in the production of polyisocyanate-modified s Polychloroprene latex foam with the pH of the latex from greater than about 11.5 to about 10.0 to 11.5 by adding an alkanol amine is set, characterized in that the polychloroprene latex with, respectively based on 100 parts by weight of latex solids, 0.5 to 3 parts by weight of a conventional, nonionic, surface-active Means with an HLB value of about 11 to 16.5 and 0.5 to 2.0 parts of an alkanol amine of the formula ij