NO134841B - - Google Patents

Description

The invention relates to cellular products made of polyurethane foam plastic. The purpose of the invention is to provide polyurethane foam plastic with a low bulk density and high absorbency, further with a very high degree of softness and with improved hydrophilic properties.

It is already well known to produce soft polyurethane foam plastics by reacting a polyisocyanate with a compound that is at least dihydroxylated, in the presence of a catalyst, a propellant and various other additives such as stabilizers, surfactants and the usual diluents

funds.

The manufacturing method is also known

of such foam plastics with open cells, possibly liquid-permeable, with a character much like natural sponge. Unfortunately, these polyurethane foams cannot replace natural sponges despite their good mechanical properties and resistance to a number of chemical substances and to bacteria, as the artificial sponges have the disadvantage that they are not sufficiently hydrophilic and have little water absorption capacity.

Various methods have already been proposed for

to avoid these disadvantages. In particular, it has been proposed to impregnate the already produced foam plastic with hydrophilic substances such as e.g. polyacrolein (French patent 1,529,512) or acrylic

polymers (French patent 1,480,562). The articles produced in this way have the disadvantage that they are expensive because they need an additional production step, that they have uneven hydrophilic properties

creates (the impregnation is difficult to make homogeneous) and only temporary such properties (the hydrophilic agent has

its to be lost with the water during repeated washing), and has insufficient mechanical properties.

Other methods avoid post-treatment of the foam but introduce mineral substances into the reaction mixture (French patent 1,147,883) or cellulose-based organic fillers (French patent 1,566,886). In these cases too, the durability of the hydrophilic character and the mechanical properties, especially the softness of the products, are not satisfactory.

Furthermore, as is well known, it has been proposed. to the mixture of hydroxyl compound and polyisocyanate, or to the hydroxyl compound before mixing, to add various substances such as e.g. a polyalkylene glycol (French patent 1,554,210), a methoxy or ethoxy polyethylene glycol (French patent 1,466,352), aldehyde alcohols (French patent 1,501,578), morpholine derivatives (French patent 1,501,616), but the improvement of the absorption capacity for water has in each case led to other disadvantages such as reduced mechanical strength, unpleasant surface structure and other defects which limit the practical application for manufactured objects of such polyurethane foam.

The known, lightweight polyurethane foams are usually produced from mixtures with a low water content and a high propellant content such as trichloromonofluoromethane or methylene chloride. These techniques are very delicate in operation and often lead to mediocre products. The use of polyether polyols which simultaneously contain ethylene oxide derivative units and propylene oxide derivative units in connection with untreated polyisocyanates leads to foam plasters with closed cells which then have to be opened during finishing. Furthermore, these compositions cannot be combined with the usual silicone oil additives, which leads to great manufacturing difficulties.

The known polyhydroxy compounds for the production of foam plastics are usually polyether polyols which originate from the condensation of one or more alkylene oxides on at least one compound which contains several active hydrogen atoms, such as e.g. a polyol, an amine, etc. (French patent 1,587,727), and may also be a mixture of several polyhydroxy compounds of this type (U.S. patent 3,457,203). Among the most commonly used alkylene oxides are ethylene oxide and propylene oxide. In the latter case, the content of ethylene oxide does not exceed 40%, as a higher content leads to major difficulties during the execution. The use of products with a high content of ethylene oxide is, however, particularly sought after by the foam plastics industry, as these are less expensive than the alkylene oxides currently used.

The present invention relates to soft polyurethane foam sheets with hydrophilic properties, obtained by reaction between a purified or an impure 2,4- and/or 2,6-toluene diisocyanate and a polyether polyol or a mixture of polyether polyols in the presence of a catalyst and a propellant comprising water and possibly another foaming agent1 such as trichlorofluoromethane, and the foam plastic is characterized by the fact that the polyether polyol included in the reaction product is based on ethylene oxide and propylene oxide, as well as an initiator containing at least 2 active hydrogen atoms, which polyether polyol contains 50-70% ethylene oxide groups expressed on a weight basis of the amount of polyether polyol, and which fulfills the following conditions: a) the average molar equivalent weight is between 800 and 2000 per hydroxyl group, b) the ratio x between the number of primary hydroxyl groups and the total number of hydroxyl groups is between 35 and 55%, c) the ratio y between the content of ethylene oxide and the content of primary hydroxyl groups is at. between 1.1 and -1.7,

with the additional condition that for values of x between 45 and 55% the ratio y must be lower than 1.3, while when the ratio y is above 1.3 the value for x must be between 35

and 45%,

d) the blanking point determined according to method AFNOR T 7 3 40 3, method B, is lower than 30,

and that polyisocyanate and polyether polyol are used in such quantities that the ratio NCO/OH, number of isocyanate groups

per number of hydroxyl groups, amounts to at least 1.

According to the invention, when the above provisions are complied with, extraordinarily soft foams are obtained compared to what is previously known, and at the same time foams with improved hydrophilic properties.

Furthermore, the practical advantage that it is possible to use crude distillation mixtures of the toluene diisocyanate must be emphasized. This type of mixture is preferred by economic

grounds and are always commercially available.

Among the polyisocyanates that can be used in the production of the foam plastics according to the invention, the toluene diisocyanate (TDI) in the form of a mixture of isomers 2-4 and 2-6 should be highlighted. This mixture preferably contains 80% by weight of 2-4 isomers and 20% by weight of 2-6 isomers, but may contain other proportions such as e.g. respectively 70 and 30% of the above isomers. The production of toluene diisocyanate leads

to a mixture which, in addition to this compound and in smaller quantities, contains heavy, oily products which can be separated by distillation, the toluene diisocyanate passing over to the top of the column. However, as stated above, you can just as easily use a partially purified product that is collected on

somewhere in the middle of the column or even an undistilled product called crude polyisocyanate as a purified top product. The practical advantage that it is possible to use crude distillation mixtures of toluene diisocyanate directly must be emphasized here. This type of mixture is preferred for economic reasons and is always available on the market.

The most important feature according to the invention is to use a polyether polyol which corresponds to requirements a) to d) above. Certain properties of the polyether polyol are decisive for achieving the results according to the invention: In the present description, polyether polyol is understood as a single polyhydroxy compound or a mixture of hydroxy compounds which has all the properties a) to d) above. In the practical implementation of the invention, a mixture of several polyether polyols and preferably two polyols which are mutually insoluble and which at the same time correspond to all the properties a) to d) will be used. The polyether polyols that are advantageously used fall into the following categories: - polyether polyols produced by statistical condensation tion of mixtures of ethylene oxide and propylene oxide with an initiator containing at least two active hydrogen atoms, which polyether polyol contains 58 to 77% ethylene oxide and 35 to 44% primary hydroxyl groups and/or - polyether polyols prepared by successive condensation of propylene oxide and then ethylene oxide on an initiator containing at least 2 active hydrogen atoms, where the polyether polyol contains 4 to 15% ethylene oxide and 35 to 60% primary hydroxyl groups.

According to the invention, good results are achieved when the ratio x is between 35 and 45% and the ratio y between 1.3

and 1.7. It has also been found that when the ratio x is equal to OHP/OHT (OH primary/OH total) increases, the ratio y is equal to OE/OHP (ethylene oxide/OH primary) will decrease.

It has thus been found that very soft polyurethane foam plastics with hydrophilic properties can be produced by starting from a polyether polyol or a mixture of polyether polyols where certain properties are outside the ranges 35 to 45% for x and 1.3 to 1.7 for y, as mentioned above. In particular, they have arrived at foam plastics with favorable properties based on polyether polyols where the number of primary hydroxyl groups in relation to the number of total hydroxyl groups is over 45%

while the ratio between ethylene oxide content and primary hydroxyl groups is below 1.3, while the other properties

a) and d) are unchanged.

For x values of between approx. 45 and 55% you should therefore

choose y values of less than approx. 1.3, while values for y of over 1.3 require corresponding x values of approx. 35 and 45%.

Among the initiators, those that contain

where at least 3 active hydrogen atoms, such as glycerol, trimethylol-

propane, pentaerythritol and sorbitol-

In the following illustrative examples of foam plastic production

ling use the following polyether polyols:

Polyether polyol A: produced by statistical condensation between diethylene glycol and a mixture consisting of 75 parts ethylene oxide and 25 parts propylene oxide. After treatment, the product has a hydroxyl number of 55, a viscosity at 37.8°C of 450 centipois and a content of 43% primary hydroxyl groups.

Polyether polyol B; prepared by statistical condensation between trimethylolpropane and a mixture consisting of 75 parts of ethylene-

oxide and 25 parts propylene oxide. After treatment, the product has an e<+-> hydroxyl number of 45, a viscosity at 37.8° of 450 centipois and a content of primary hydroxyl groups of 38%.

Polyether polyol C: produced by successive condensation between trimethylolpropane and 3900 parts by weight of propylene oxide, then 450 parts by weight of ethylene oxide. After treatment, the product has a hydroxyl number of 36, a viscosity at 37.8° of 300 centipois and a content of 45% primary hydroxyl groups.

Polyether polyol D: produced by stepwise binding to glycerol

of 3470 parts by weight propylene oxide and 91 parts by weight ethylene oxide. The product has a hydroxyl number of 46, contains 2.5% ethylene oxide and 20% primary hydroxyl groups,

Polyether polyol F: produced by statistical binding to perita-erythritol of a mixture of 3,700 parts by weight of ethylene oxide and 1,064 parts by weight of propylene oxide. The end product has a hydroxyl number of 45.7, contains 75% ethylene oxide and 43% primary hydroxyl groups.

Polyether polyol F: produced by stepwise binding to ethylene diamine of 3010 parts by weight propylene oxide and G30 parts by weight ethylene oxide. The final<p>roduct has a hydroxyl number of 60, contains 17% ethylene oxide and 56% primary hydroxyl groups. Polyether polyol G: produced by stepwise binding to ethylene glycol of first a mixture of 470 parts by weight propylene oxide and 1600 parts by weight ethylene oxide and then 66 parts by weight propylene oxide. The product has a hydroxyl number of 51, contains 74% ethylene oxide and 20% primary hydroxyl groups.

Polyether polyol H: produced by stepwise binding to propylene glycol of 1,834 parts by weight of propylene oxide, then 290 parts by weight of ethylene oxide. The final product has a hydroxyl number of 51, contains 13% ethylene oxide and 31% primary hydroxyl groups. Polyether polyol I: prepared by statistical condensation on trimethylpropane of a mixture containing 75 parts by weight of ethylene oxide and 2.5 parts by weight of propylene oxide. The product has a hydroxyl number of 42, a viscosity at 37.8°C of 470 eps and contains 50% primary hydroxyl groups.

Polyether polyol J: produced by stepwise condensation on trimethylpropane of 3,900 parts by weight of propylene oxide, then 450 parts by weight of ethylene oxide. The product has an OH number of 36, a viscosity at 37.8 C of 320 eps and contains 50% primary hydroxyl groups.

Another feature of the production of the foam plastics according to the invention, in combination with the use of the specified polyether polyol, consists in adjusting the relative proportions of polyisocyanate and polyether polyol in such a way that a ratio between the NCO/OH groups equal to or higher than 1.

A special feature in the production of the foam plastics

according to the invention further consists in that the propellant or expansion agent consists of water and possibly another propa-

duct which is already known and used for this purpose for polyurethane foam blends.

The person skilled in the art knows various products that are added to polyurethane foam landings, as well as the manufacturing technique for such foams. One refers to e.g. to the book by Saunders and Frisch "Folyurethanes, Chemistry and Technology", Part II, Interscience,

New York, 1964.

In the following, the invention shall be illustrated without limitation to the examples shown, where quantity ratios are stated on a weight basis, where nothing else is stated. The properties of the foam plastic are measured according to the following methods:

Measure for "resilience".

The measurement takes place according to the method described in the ASTM D standard

1564-62 T. On a sample block of the foam plastic with a rectangular shape 400 mm x 400 mm x 100 mm, a round disc is placed in an "indentometer" with a surface area of 322.5 cm 2. Resilient

the heat is expressed by the load in kilograms that must be placed on the plate to achieve compressions of respectively 25, 40, 50 and 65%.

Measures of porosity

Through a tube of 22 mm diameter, depressed 10 mm in

a piece of foam plastic with dimensions 100 x 100 x 50 mm, a constant air flow of 8 l/min is introduced. The pressure drop is read on a water manometer shaped like a U, and the resistance to the air flow through the piece of foam plastic is expressed in millimeters of water height, which corresponds to the difference in level between the two water surfaces in the U-tube.

Measurement of the drying ability

50 mm of water is distributed as evenly as possible on a four-

angular surface with side edge 50 cm. You start drying with the two largest sides of a foam sponge with the normal sponge sizes 14 x 9 x 5 cm and continue for 20 seconds. The absorption power is measured as the percentage of water that is absorbed in relation

to the amount that remains.

Measure for maximum absorption

A sample sponge of 14 x 9 x 5 cm is placed on a grid: in: the shape of a U. The whole thing is weighed, then introduced into a water container where the sponge is completely covered by water. You squeeze the sponge once and let it go back. You draw it

whole and let it drain for 2 minutes. Weigh again

■'. substrate plus sponge. The difference in weight denotes the maximum absorption capacity of water. The results are expressed as the ratio between the amount of water absorbed and the weight of the sponge.

The following examples illustrate the advantages of the invention. ;■.0

Examples 1-4

Using a stirrer at a speed of 2800 rpm. polyether-polyol A is mixed with polyether-polybl C and the usual additives listed in table I. After homogenization of the mixture, the amount of toluene diisocyanate 80/20 is introduced (which consists of 80 and 20% isomers 2-4 and 2-6, respectively) which corresponds to the numerical ratio NCO/OH listed in Table I. The stirring is continued for a few seconds and then the mixture is poured into a cubic form with a side edge of 40 cm. The mixture is foamed and expanded and when the reaction is finished, the foam is treated in a heating chamber at 70°C for 15 minutes. After 24 hours of storage, the physical properties listed in Table I are measured. For all tests, 850 parts by weight of polyether polyol A and 150 parts of polyether polyol C are used.

The mixture has the following characteristic properties:

These examples show that mari, while retaining /excellent hydrophilic properties, can vary the degree of softness of the foam plastic by varying the NGO/OH ratio, the catalysis system

•or the amount of water.

Examples 5 to 9

The tests are carried out in a Martin Sweet machine with a total output of 15 kg/min. T <*> '

Mixtures of polyether polyol B and C are used in the ratio 7 8 parts B to 2 2 parts C, except in example 6. The mixture has the following properties:

In example 6, 70 parts polyether polyol B and 30 parts polyether polyol C are used. The mixture is then slightly changed:

In example 7, a toluene diisocyanate containing 65% 2-4 isomers and 35% 2-6 isomers is used. In examples 8 and 9, a crude toluene diisocyanate containing 43% NCO groups, marketed under the name "Lilene F", is used.

The results obtained are summarized in table II.

Examples 10, 11 and 12

In these examples, the foams are produced using trichlorofluoromethane as a propellant. Table III reproduces the measured properties for the foam plastics.

Example 13

You proceed as in example 5, except that you change the quantity ratio between polyether polyol B and C, which gives the following composition:

The mixture of the two polyethers in the stated proportions contains 39.5% primary OH groups, an OH number of 44.6, a flash point of 27 and a ratio OE/OH.P of 1.75, i.e. outside the limits is assumed according to the invention.

The foam begins to rise, then subsides. A change of the catalyst or the silicone oil does not improve the situation.

Example 14..'

You proceed as in example 5, but change the ratio

between polyethers B and C to the following composition:

The mixture of the tb polyethers in the specified proportions contains 41% primary OH groups, has a hydroxyl number of 41.5, a bi-increase point of 26 and a ratio OE/OH.P of 1.20, i.e. outside the limits assumed according to the invention. The foam expands and then collapses by 50%. A significant change to the catalyst system or the content of silicone can prevent the collapse, but the foam contains closed cells.

Examples 15 and 16

These examples illustrate the use of other polyether-polyol mixtures. These mixtures are characterized by the following data: 'i

The compositions used and the properties of the manufactured foam plastics are listed in Table IV.

It will be seen that all the mixtures of polyether polyols which correspond to the specifications of the invention lead to foam plastics with extraordinary softness. The following examples show that the properties relating to the mixture of polyether polyols which are emphasized according to the invention are necessary. If one of the conditions is not met, you get either no foam or unusable foam masses, regardless of the other conditions.

Example 17

The following mixture is prepared:

The mixture of the two polyethers in the specified proportions gives the following average properties:

The breaking point is thus outside the limits assumed according to the invention.

The foam expands and then collapses. A change to the catalytic system does not lead to any improvement.

Example 18

The following mixture is prepared:

This mixture of the two polyethers gives the following average data:

The ratio OE/OH.P is thus outside the assumed ones

borders.

The foam expands, but then collapses. A change to the catalytic system does not lead to any improvement.

Example 19

The following mixture is prepared:

The mixture of the two polyethers in specified proportions

§ir the following average properties:

The foam expands but collapses. A change

of the catalysis system results in no improvement.

Example 20

A mixture of polyether polyols I and J is used, namely 85 parts I and 15 parts J. The mixture has the following data:

Example 21

A mixture of polyether polyols (I) and (J) containing 7 8 I and 22 parts J is used. The mixture has the following data:

Example 2 2

A mixture of polyether polyols I and J is used, namely a mixture of 70 parts I and 30 parts J. The mixture has the following data:

The polyether polyols in examples 1 to 3 were used for the production of polyurethane foams in a machine of the Martin Sweet type.

The recipes and properties for the manufactured foam plastics are summarized in the following table:

Claims (2)

1. Soft polyurethane foam plastic with hydrophilic properties, obtained by reaction between a purified or an impure 2,4- and/or 2,6-toluene diisocyanate and a polyether polyol or a mixture of polyether polyols in the presence of a catalyst and a propellant comprising water and optionally a other foaming agent such as trichlorofluoromethane, characterized in that the polyether polyol included in the reaction product is based on ethylene oxide and propylene oxide as well as an initiator containing at least 2 active hydrogen atoms, which polyether polyol contains 50-70% ethylene oxide groups expressed on a weight basis of the amount of polyether polyol, and which meet the following conditions! a) the average molar equivalent weight is between 800 and 2000 per hydroxyl group, b) the ratio x between the number of primary hydroxyl groups and the total number of hydroxyl groups is between 35 and 55%, c) the ratio y between the content of ethylene oxide and the content of primary hydroxyl groups is between 1.1 and 1.7, with the additional condition that for values of x between 45 and 55%, the ratio y must be lower than 1.3, while when the ratio y is above 1.3, the value for x must be between 35 and 45%, d) the fading point determined according to the method AFNOR T 7 3 40 3, method B, is lower than 30, and that polyisocyanate and polyether polyol are used in such quantities that the ratio NCO/OH, the number of isocyanate groups per number of hydroxyl groups, amounts to at least 1. 2. Polyurethane foam plastic according to claim 1, characterized in that mixtures from the following classes are used as polyether polyols: polyether polyols produced by statistical condensation between mixtures of ethylene oxide and propylene oxide with an initiator containing at least two active hydrogen atoms, which polyether polyol contains 58 to 77% ethylene oxide and 35 -44% primary hydroxyl groups and/or polyether polyols produced by stepwise condensation of propylene oxide and then ethylene oxide on an initiator containing at least two active hydrogen atoms, which polyether polyol contains 4-15% ethylene oxide and 35-60% primary hydroxyl groups, in such quantities that the mixture as a whole fulfills the conditions specified under requirement 1.