Polyurethane foam

Abstract

A polyurethane foam is disclosed having unique load bearing characteristics rendering it suitable for a variety of applications. The foam exhibits high surface-softness and smoothness properties, making it well-suited for use in articles such as pillows and mattress toppers. However, upon continued application of pressure, the resilience of the foam increases sharply, translating into a remarkable support characteristics that make the foam suitable for use in the seat portions of chairs and sofas, as well as in the base portion of mattresses. The foams therefore address the limitations of conventional, high-resilience and visco-elastic polyurethane foams. A process of making the foam and its use in various articles is also disclosed.

Claims

1. A process for the preparation of a polyurethane foam, the process comprising the steps of: a) mixing together the following ingredients in the amounts specified: i. at least one polyol having an average molecular weight of 7,500-8,500 Da, wherein the polyol has an OH functionality of 2-4 and an OH value of 26-30, ii. at least one methylene diphenyl diisocyanate having an NCO content of 29-31%, wherein the amount of diisocyanate relative to the amount of polyol is sufficient to give an ISO index of 72-110, wherein the methylene diphenyl diisocyanate is a modified methylene diphenyl diisocyanate, iii. at least one surfactant in an amount of 0.5-0.75 per hundred parts polyol, iv. at least one blowing agent in an amount of 1.5-8.0 per hundred parts polyol, v. at least one cell opener in an amount of 2.0-5.5 per hundred parts polyol, vi. at least one amine catalyst in an amount of 0.2-0.55 per hundred parts polyol, vii. at least one tin catalyst in an amount of 0.01-0.1 per hundred parts polyol, viii. water in an amount of 1.5-3.3 per hundred parts polyol, and ix. optionally at least one flame retardant in an amount of 6.5-14.0 per hundred parts polyol, wherein when a flame retardant is used, it is used in conjunction with a melamine-based flame-retardant synergist, wherein the melamine-based flame retardant synergist, when present, is present in an amount of 9.0-17.0 per hundred parts polyol; b) curing the mixture resulting from step a); wherein, in step a), the polyol is fed to a mixer at a rate of 100-140 kg/min.

2. The process of claim 1, wherein the ingredients specified in step a) are mixed at a speed of 2,000-8,000 rpm.

3. The process of claim 1, wherein the polyol is a polyether polyol and/or has an OH functionality of 2.8-3.2.

4. The process of claim 1, wherein the amine catalyst is triethylene diamine.

5. The process of claim 1, wherein in step a), the at least one flame retardant is present in an amount of 6.5-14.0 per hundred parts polyol, or the flame retardant is present in an amount of 8.0-13.5 per hundred parts polyol.

6. The process of claim 1, wherein the tin catalyst is an alkyl carboxylate.

7. The process of claim 1, wherein those ingredients mixed in step a) further comprise at least one of a chain extender and a cross-linker in an amount of 0.2-1.5 per hundred parts polyol, and the chain extender and/or cross-linker is diethanol amine.

8. The process of claim 1, wherein in step b), the mixture resulting from step a) is cured in an atmosphere of air.

9. The process of claim 1, wherein in step a), the polyol is fed to a mixer at a rate of 100-140 kg/min, or the methylene diphenyl diisocyanate is fed to a mixer at a rate of 30-80 kg/min, or the surfactant is fed to a mixer at a rate of 45-85 kg/min, or the amine catalyst is fed to a mixer at a rate of 20-50 kg/min, or water is fed to a mixer at a rate of 2-6 kg/min.

10. The process of claim 1, wherein the process comprises the steps of: a) mixing together the following ingredients in the amounts specified: i. at least one polyol having an average molecular weight of 7,500-8,500 Da, wherein the polyol has an OH functionality of 2.8-3.2 and an OH value of 26-30, ii. at least one methylene diphenyl diisocyanate having an NCO content of 29-31%, wherein the amount of diisocyanate relative to the amount of polyol is sufficient to give an ISO index of 72-100, wherein the methylene diphenyl diisocyanate is a modified methylene diphenyl diisocyanate, iii. at least one surfactant in an amount of 0.55-0.75 per hundred parts polyol, iv. at least one blowing agent in an amount of 4.0-8.0 per hundred parts polyol, v. at least one cell opener in an amount of 2.0-5.5 per hundred parts polyol, vi. at least one amine catalyst in an amount of 0.2-0.55 per hundred parts polyol, vii. at least one tin catalyst in an amount of 0.01-0.05 per hundred parts polyol, viii. water in an amount of 1.5-3.3 per hundred parts polyol, and ix. at least one of a chain extender and a cross-linker in an amount of 0.6-1.2 per hundred parts polyol, x. optionally at least one flame retardant in an amount of 6.5-14.0 per hundred parts polyol, wherein when a flame retardant is used, it is used in conjunction with a melamine-based flame-retardant synergist, wherein the melamine-based flame retardant synergist, when present, is present in an amount of 9.0-17.0 per hundred parts polyol; b) curing the mixture resulting from step a) to form a polyurethane foam having a density of 40-60 kg/m.sup.3 wherein, in step a), the polyol is fed to a mixer at a rate of 110-130 kg/min.

Description

EXAMPLES

(1) One or more examples of the invention will now be described, for the purpose of illustration only, with reference to the accompanying figures, in which:

(2) FIG. 1 shows a continuous foam forming process used in the preparation of the foams of the examples and comparative examples. The process parameters were: mixing head pressure—0.3 MPa; air injection—0.1 L/min; raw materials temperature—22° C.; foaming speed—4.0 m/min; mixing head mixing speed—5000 rpm.

(3) FIG. 2 shows a box foaming (discontinuous) process.

MATERIALS AND METHODS

(4) In following examples, the components used were:

(5) Polyol A: Caradol SC56-02 (560H value, 3000 mwt.), available from Shell Chemicals Company;

(6) Polyol B: GLR2000 (2400H value, 700 mwt.), available from Sinopec Shanghai Gaoqiao Chemical Company;

(7) Active Polyol C: polyol 330N (330H value 5000 mwt), available from Sinopec Shanghai Gaoqiao Chemical Company;

(8) Active polyol D: polyol GEP828 (28 OH value 8000 mwt) from Sinopec Shanghai Gaoqiao Chemical Company;

(9) Flame retardant FR508, available from Yoke Chemicals Company;

(10) Flame retardant synergist: melamine;

(11) Surfactant A: B2470, available from Evonik;

(12) Amine catalyst: Niax A1 (available from Momentive) and Dabco 33-LV (available from Air product);

(13) Tin Catalyst: K29 from Enovik;

(14) Toluene diisocyanate (TDI) is available from BASF;

(15) Modified methylene diphenyl diisocyanate (MDI) 6510, available from Huntsmen Chemicals Company (NCO % 29.9);

(16) Surfactant B: B8002, available from Evonik;

(17) Surfactant L5333 from Momentive;

(18) Cell opener: PK101, available from Fushun Chemical Company;

(19) Cell opener: KZ28, available from Nanjing Aosai Chemical Co.

(20) Blow agent: Methylene chloride;

(21) Chain extender/cross linker: Diethanol amine.

(22) In the following examples, foams were prepared using the continuous foaming process depicted in FIG. 1.

Example 1

(23) Having regard to Table 1 below, a flexible polyurethane foam was prepared according to the continuous foaming process depicted in FIG. 1 using the ingredients and amounts specified.

(24) TABLE-US-00001 TABLE 1 Ingredients used in the preparation of flexible polyurethane foam of Example 1 Flow rate to mixer Ingredients Parts/php* head (kg/min) Active polyol D 100  120 Flame retardant FR 508 7 8.4 Melamine 10  12 H.sub.2O   3.2 3.84 Methylene chloride 7 8.4 Surfactant L5333   0.55 0.66 Amine catalyst   0.3 0.36 Tin Catalyst   0.03 0.04 Cell opening agent 3 3.6 Diethanol amine   0.8 0.96 Modified MDI  40** 48 *per hundred parts polyol; **amount of MDI was sufficient to give an ISO index of 75.

(25) After forming, the foam was left to cure at room temperature for 72 hours.

(26) The properties (density, sag value and fire retardancy) of the cured flexible polyurethane foam of Example 1 were then assessed. The results are presented in Table 2 below.

(27) TABLE-US-00002 TABLE 2 Density, sag value and fire retardancy properties of flexible polyurethane foam of Example 1 Foam density (kg/m.sup.3) 45 IFD25%/N 22.1 IFD40%/N 34.8 IFD65%/N 72.2 Sag value (IFD65%/IFD25%) 3.3 BS5852 crib5 fire retardancy Pass, 34 g mass loss

(28) As can be seen from the data presented in Table 2, the IFD25% of the flexible polyurethane foam of Example 1 is 22.1N, which is substantially lower than that observed for conventional, HR and visco-elastic polyurethane foams. This value reflects the high surface softness and smoothness of the flexible polyurethane foam of Example 1 when compared with other polyurethane foams. However in spite of the high surface softness and smoothness, the data presented in Table 2 illustrate that the sag value of the flexible polyurethane foam—which is typically used to gauge the level of comfort offered by a foam—is 3.3, which is notably higher than that observed for conventional, HR and visco-elastic polyurethane foams. This means that the foam of Example 1, despite having excellent surface softness and smoothness characteristics, also offers remarkable support, without excessive sinking. This is likely due to the fact that whilst the upper surface of the foam is soft, the firmness of the foam increases sharply upon continued application of pressure.

(29) In addition to the above, the flexible polyurethane foam of Example 1 meets the BS5852 crib 5 flammability standard—a UK requirement which is perhaps the most stringent of all international flame retardancy standards. Achieving high surface-softness, high sag value and BS5852 crib 5 compliance in a single polyurethane foam is particularly advantageous.

Comparative Example 2—Conventional Flame-Retardant Polyurethane Foam

(30) Having regard to Table 3 below, a flexible conventional flame-retardant polyurethane foam was prepared according to the continuous foaming process depicted in FIG. 1 using the ingredients and amounts specified.

(31) TABLE-US-00003 TABLE 3 Ingredients used in the preparation of flexible polyurethane foam of Comparative Example 2 Flow rate to mixer Ingredients Parts/php* head (kg/min) Polyol, A 100 150 Flame retardant FR508 15 22.5 Melamine 30 45 H.sub.2O 3.2 4.8 Methylene chloride 3 4.5 Surfactant A 1.2 1.8 Amine catalyst 0.3 0.45 Tin Catalyst 0.24 0.36 TDI (NCO %: 48.3) 45.6** 68.4 *per hundred parts polyol; **amount of TDI was sufficient to give an ISO index of 115.

(32) After forming, the foam was left to cure at room temperature for 72 hours.

(33) The properties (density, sag value and fire retardancy) of the cured flexible polyurethane foam of Comparative Example 2 were then assessed. The results are presented in Table 4 below.

(34) TABLE-US-00004 TABLE 4 Density, sag value and fire retardancy properties of flexible polyurethane foam of Comparative Example 1 Foam density (kg/m.sup.3) 32 IFD25%/N 85.5 IFD40%/N 123.2 IFD65%/N 189.5 Sag value (IFD65%/IFD25%) 2.2 BS5852 crib5 Pass, 32 g mass loss

(35) The foam of Comparative Example 2 is a typical BS5852 Crib5-compliant conventional polyurethane foam. Despite being fire retardant, the conventional polyurethane foam of Comparative Example 2 has an extremely high IFD25% value, which manifests itself as poor surface softness characteristics. As a consequence, the foam of Comparative Example 2 is only suitable for use as a base layer in mattresses, and cannot be used in the upper surface on which a consumer sleeps.

Comparative Example 3—Visco-Elastic Polyurethane Foam

(36) Having regard to Table 5 below, a flexible polyurethane visco-elastic foam was prepared according to the continuous foaming process depicted in FIG. 1 using the ingredients and amounts specified.

(37) TABLE-US-00005 TABLE 5 Ingredients used in the preparation of flexible polyurethane foam of Comparative Example 3 Flow rate to mixer Ingredients Parts/php* head (kg/min) Polyol A 50 75 Polyol B 50 75 H.sub.2O 2 3 Surfactant B 0.8 1.2 Amine catalyst 0.4 0.6 Tin Catalyst 0.08 0.12 cell open agent 4 6 TDI (NCO %: 48.3) 37.2** 55.8 *per hundred parts polyol; **amount of TDI was sufficient to give an ISO index of 88.

(38) After forming, the foam was left to cure at room temperature for 72 hours.

(39) The properties (density, sag value and fire retardancy) of the cured flexible polyurethane visco-elastic foam of Comparative Example 3 were then assessed. The results are presented in Table 6 below.

(40) TABLE-US-00006 TABLE 6 Density, sag value and fire retardancy properties of flexible polyurethane foam of Comparative Example 3 Foam density (kg/m.sup.3) 43 IFD25%/N 30.4 IFD40%/N 43.6 IFD65%/N 60.2 Sag value (IFD65%/IFD25%) 2.0 BS5852 crib5 Fail, burnt out

(41) The foam of Comparative Example 3 is a visco-elastic foam that is widely used in pillows, mattresses and mattress toppers. Although visco-elastic foams offer softness and are able to conform to the body in order to distribute body pressure evenly, they suffer from the standpoint of providing sufficient support. As can be seen from the data presented in Table 6, sag value of the visco-elastic foam of Comparative Example 3 is only 2.0, which translates to a consumers feeling that they are sunken into the foam, rather than being properly supported by it.

Comparative Example 4—Flame-Retardant HR Polyurethane Foam

(42) Having regard to Table 7 below, a flexible polyurethane HR foam was prepared according to the continuous foaming process depicted in FIG. 1 using the ingredients and amounts specified.

(43) TABLE-US-00007 TABLE 7 Ingredients used in the preparation of flexible polyurethane foam of Comparative Example 4 Flow rate to mixer Ingredients Parts/php head (kg/min)* Active polyol C 100 150 Flame retardant 8 12 Melamine 15 18 H.sub.2O 3 4.5 Methylene chloride 3 4.5 Surfactant C 0.6 0.9 Amine catalyst 0.3 0.45 Tin Catalyst 0.1 0.15 Diethanol amine 1 1.5 TDI (NCO %: 48.3) 40.2** 60.3 *per hundred parts polyol; **amount of TDI was sufficient to give an ISO index of 110.

(44) After forming, the foam was left to cure at room temperature for 72 hours.

(45) The properties (density, sag value and fire retardancy) of the cured flexible polyurethane HR foam of Comparative Example 4 were then assessed. The results are presented in Table 8 below.

(46) TABLE-US-00008 TABLE 8 Density, sag value and fire retardancy properties of flexible polyurethane foam of Comparative Example 4 Foam density (kg/m.sup.3) 31 IFD25%/N 67.4 IFD40%/N 100.5 IFD65%/N 182 Sag value (IFD65%/IFD25%) 2.7 BS5852 crib5 Pass, 35 g mass loss

(47) The foam of Comparative Example 4 is a typical BS5852 Crib5-compliant HR polyurethane foam. The foam exhibits good support properties, due in part to the higher molecular weight of polyol used in comparison to conventional and visco-elastic foams, which makes the HR foam widely useable in the seat portion of chairs and sofas. However, the HR polyurethane foam of Comparative Example 4 has an extremely high IFD25% value, which manifests itself as poor surface softness characteristics. As a consequence, the foam of Comparative Example 4 is unsuitable for use in pillows and mattress toppers, wherein high surface-softness is necessary.

Example 5

(48) Having regard to Tables 9 and 10 below, various polyurethane foams were prepared according to the continuous foaming process depicted in FIG. 1 using the ingredients and amounts specified.

(49) TABLE-US-00009 TABLE 9 Composition and properties of various polyurethane foams Foam 1 2* 3 4* 5 6 FOAM COMPOSITION Active polyol D 100 100 100 100 100 100 Cell opener 3 3 3 3 3 5 KZ28/phpp Flame retardant 3 20 12 12 12 0 FR508/phpp Melamine/phpp 15 15 15 15 15 0 Silicone 0.7 0.7 0.7 0.7 0.7 0.7 surfactant L5333/phpp Amine 0.5 0.5 0.5 0.5 0.5 0.5 catalyst/phpp Tin catalyst/ 0.05 0.05 0.05 0.05 0.05 0.05 phpp H2O/phpp 2 2 4 1 2 2 Blow agent/ 5 5 5 5 5 2 phpp TEOA/phpp 0.6 0.6 0.6 0.6 0.6 0.6 ISO index** 90 90 90 90 90 100 FOAM PROPERTIES Cream time/s 10 12 8 30 10 8 Full rising 163 183 125 N/A 172 159 time/s Foam density/ 54.2 60.4 36.3 N/A 57.2 55.2 kg/m3 IFD 25/40/ 29/43/91 29.3/41.1/78.2 39.5/62/110.2 N/A 25.2/41.3/77.2 23.5/40.3/79.2 65(N) Sag value 3.1 2.67 2.8 N/A 3.1 3.4 Ball 62 52 50 N/A 65 69 resilience/% Overall foam 5 2 3 N/A 5 5 physical performance (1-5; 1 = poor, 5 = excellent) FR BS5852 crib Fail. Foam continued Pass. Mass Fail. Foam continued N/A Pass. Mass Fail. Foam continued 5 test burning after 10 mins. loss 38 g burning after 10 mins. loss 35 g burning after 10 mins. Mass loss > 60 g after 4 mins Mass loss > 60 g after 4 mins Mass loss > 60 g 35 sec 55 sec Comments Foam exhibits BS5852 crib 5 Higher water Low water BS5852 crib 5 Foam exhibits excellent excellent compliant, but content gave rise content compliant physical properties. physical high content of to certain defects hampered foam and excellent Lack of flame retardant properties. flame retardant in foam, and rising. Sample physical meant foam was not Not enough flame compromised overall poorer not cured properties BS5852 crib retardant to confer physical prop- physical 5 compliant BS5852 crib 5 erties of foam properties compliance *comparative example; **ISO index achieved by adding appropriate amount of modified MDI; phpp-per hundred parts polyol

(50) TABLE-US-00010 TABLE 10 Composition and properties of various polyurethane foams Foam 7* 8* 9* 10* 11* 12* FOAM COMPOSITION Active polyol D 100 100 100 100 100 100 Cell opener 3 3 3 3 3 3 KZ28/phpp Flame retardant 12 12 12 12 12 12 FR508/phpp Melamine/phpp 15 15 15 15 15 15 Silicone surfactant 0.7 0.7 0.7 0.7 0.1 2 L5333/phpp Amine 0.1 1 0.5 0.5 0.5 0.5 catalyst/phpp Tin catalyst/phpp 0.05 0.05 0.05 0.05 0.05 0.05 H2O/phpp 2 2 2 2 2 2 Blow agent/phpp 5 5 5 5 5 2 TEOA/phpp 0.6 0.6 0.6 0.6 0.6 0.6 ISO index** 90 90 70 120 90 90 FOAM PROPERTIES Cream time/s 40 2 16 8 11 10 Full rising time/s NA 81 192 150 NA 172 Foam density/ NA NA 65.2 55.2 NA NA kg/m3 IFD 25/40/65(N) NA NA 14.2/24.2/45.2 40.4/65.8/110.8 NA NA Sag value NA NA 3.2 2.7 NA NA Ball resilience/% NA NA 53 52 NA NA Overall foam NA 1 2 2 1 1 physical performance (1-5; 1 = poor, 5 = excellent) FR BS5852 NA NA Fail. Foam continued Pass. Mass NA NA crib 5 test burning after 10 mins. loss 28 g Mass loss > 60 g after 3 mins 56 sec Comments Insufficient Excessive amount Low ISO index High ISO index Insufficient amount Excessive amount of amount of of amine catalyst resulted in overly resulted in overly of surfactant led to surfactant led to amine catalyst caused foam to soft foam having firm foam having larger cells, causing closed cell structure, for foam rise too quickly, poor support a closed cell foam collapse while causing foam shrinkage to rise causing splitting characteristics. structure and rising after curing Flame retardancy poor surface also compromised smoothness *comparative example; **ISO index achieved by adding appropriate amount of modified MDI; phpp-per hundred parts polyol

(51) The results presented in Tables 9 and 10 illustrate the effect of varying the amount of the various ingredients of the foam.

(52) While specific embodiments of the invention have been described herein for the purpose of reference and illustration, various modifications will be apparent to a person skilled in the art without departing from the scope of the invention as defined by the appended claims.