JP2007106881A - Method for producing rigid polyurethane foam with open-cell structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily producing a rigid polyurethane foam with an open-cell structure having reduced closed cell rate, increasing air flow, and expressing an excellent acoustic property. <P>SOLUTION: The rigid polyurethane foam with open-cell structure is produced by reacting raw material for polyurethane foam comprising polyols, polyisocyanates, catalysts, foaming agents and foam breaker, and then foaming and curing. In the process, polyisocyanates substantially comprising a modified diphenylmethane diisocyanate is used. The foam breaker which is obtained by addition polymerization of a mixture of a triol with a propylene oxide and an ethylene oxide having ≥60 mass% of the ethylene oxide content, is used. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a rigid polyurethane foam having an open-cell structure, particularly excellent in sound absorption characteristics, and having an open-cell structure that is suitably used as a base material for ceilings in automobile interior materials.

  Conventionally, soft polyurethane foams with an open-cell structure have been used in applications such as sound absorbing materials, but the base materials for ceilings and sun visors as interior materials for automobiles lack hardness and strength. And use was restricted. In order to eliminate such drawbacks, rigid polyurethane foams having an open cell structure have been proposed. Such hard polyurethane foams are used in the above applications because they have good sound absorption characteristics, excellent mechanical strength, and excellent room temperature moldability and thermoformability.

The present applicant has already filed an application for a rigid polyurethane foam having this type of open cell structure (see, for example, Patent Document 1). That is, the hard polyurethane foam has an open cell structure, an average cell diameter of 0.5 to 10 mm, and contains an antifoaming agent component. This rigid polyurethane foam has a large cell diameter and has good sound absorption characteristics because the cells communicate with each other.
Japanese Patent Laying-Open No. 2005-60414 (pages 2 and 3)

  However, the rigid polyurethane foam described in Patent Document 1 is foamed by blending an antifoaming agent with the polyurethane foam raw material, and in that case, the cell at the time of foaming is balanced by the balance between hydrophilicity and hydrophobicity. Therefore, the basic skeleton of polyurethane is not modified. For this reason, it is difficult to control the formation of cells as a whole foam, especially in the case of rigid polyurethane foam, compared to soft polyurethane foam, it improves cell connectivity and at the same time improves the mechanical strength of the foam. It is difficult to control. Therefore, the closed cell ratio of the foam cannot be sufficiently suppressed, in other words, the cell connectivity cannot be sufficiently increased, and there is a limit to increase in the air flow rate. As a result, the conventional rigid polyurethane foam has a limit in sound absorption characteristics and is not fully satisfactory.

  Accordingly, an object of the present invention is to provide an open cell that can easily produce a rigid polyurethane foam that has a small closed cell ratio, can increase the air flow rate, and can exhibit excellent sound absorption characteristics. It is providing the manufacturing method of the rigid polyurethane foam which has a structure.

  To achieve the above object, the method for producing a rigid polyurethane foam having an open-cell structure according to claim 1 is a polyurethane foam comprising a polyol, a polyisocyanate, a catalyst, a foaming agent and a foam breaker. A method for producing a rigid polyurethane foam having an open cell structure by reacting a raw material of a body, foaming and curing, wherein the polyisocyanate is mainly composed of modified diphenylmethane diisocyanate, The agent is characterized in that it is obtained by mixing propylene oxide and ethylene oxide with triol, and addition-polymerizing a mixture having an ethylene oxide content of 60% by mass or more in the mixture.

  The method for producing a rigid polyurethane foam having an open cell structure according to claim 2 is the invention according to claim 1, wherein the content of the foam breaker is 3 to 10 parts by mass per 100 parts by mass of polyols. It is characterized by being.

  The method for producing a rigid polyurethane foam having an open-cell structure according to claim 3 is the invention according to claim 1 or 2, wherein the modified diphenylmethane diisocyanate is urethane-modified diphenylmethane diisocyanate. It is a feature.

  The method for producing a rigid polyurethane foam having an open cell structure according to claim 4 is the invention according to any one of claims 1 to 3, wherein a trifunctional or higher functional crosslinking agent is used in the raw material. It is characterized by containing.

  The method for producing a rigid polyurethane foam having an open cell structure according to claim 5 is the invention according to any one of claims 1 to 4, wherein the polyols, the foaming agent, and the foam breaker are used. The isocyanate index which represents the equivalent ratio of the isocyanate group of the polyisocyanate to the active hydrogen group as a percentage is 100 to 120.

According to the present invention, the following effects can be exhibited.
In the method for producing a rigid polyurethane foam having an open cell structure according to claim 1, the polyisocyanate is mainly composed of modified diphenylmethane diisocyanate, and the foam breaker is a triol containing propylene oxide and ethylene oxide. And a mixture having an ethylene oxide content of 60% by mass or more in the mixture is subjected to addition polymerization. Such a foam-breaking agent is obtained by mixing propylene oxide and ethylene oxide with triol and subjecting the mixture having an ethylene oxide content of 60% by mass or more to addition polymerization. Use of such a highly hydrophilic foam-breaking agent suppresses the formation of cells during foaming, increases the cell diameter, and increases the tendency of the cells to break up and communicate with each other. Moreover, since the foam breaker has a plurality of hydroxyl groups, it reacts with polyisocyanates and is incorporated into the skeleton of the foam. On the other hand, the modified diphenylmethane diisocyanate promotes cross-linking of the foam and forms a sufficient skeleton as a rigid polyurethane foam.

  As a result, the rigid polyurethane foam has a small closed cell ratio, can increase the air flow rate, and can exhibit excellent sound absorption characteristics. And such a hard polyurethane foam can be easily manufactured by using the said specific foam breaker and polyisocyanate as a raw material.

  In the method for producing a rigid polyurethane foam having an open-cell structure according to claim 2, the content of the foam breaker is 3 to 10 parts by mass per 100 parts by mass of polyols. In addition to the effect of the invention, the effect of the foam breaker can be sufficiently exhibited.

  In the method for producing a rigid polyurethane foam having an open-cell structure according to claim 3, since the modified diphenylmethane diisocyanate is urethane-modified diphenylmethane diisocyanate, the effect of the invention according to claim 1 or 2 is achieved. In addition, the urethane skeleton of the foam can be made more satisfactory.

  In the method for producing a rigid polyurethane foam having an open-cell structure according to claim 4, the raw material contains a trifunctional or higher functional cross-linking agent. Therefore, the invention according to any one of claims 1 to 3 In addition to the above effect, the cross-linked structure of the foam can be made dense, and physical properties such as compressive strength can be enhanced.

  In the method for producing a rigid polyurethane foam having an open-cell structure according to claim 5, the isocyanate index is 100 to 120. For this reason, in addition to the effects of the invention according to any one of claims 1 to 4, a hard segment can be sufficiently formed in the polyurethane, and physical properties such as compressive strength of the hard polyurethane foam are improved. Can do.

In the following, embodiments that are considered to be the best of the present invention will be described in detail.
The method for producing a rigid polyurethane foam having an open-cell structure (hereinafter also simply referred to as a foam) according to the present embodiment uses a polyurethane foam raw material containing polyols, polyisocyanates, a catalyst, a foaming agent and a foam breaker. It is a method for producing a rigid polyurethane foam having an open cell structure by reacting, foaming and curing. At that time, the polyisocyanates are mainly composed of modified diphenylmethane diisocyanate. Furthermore, the foam breaker is obtained by mixing propylene oxide and ethylene oxide with triol, and addition polymerizing a mixture having an ethylene oxide content of 60% by mass or more in the mixture.

First, the raw material of a polyurethane foam is demonstrated.
The polyols are not particularly limited, and for example, polyether polyol or polyester polyol is used. Polyether polyols include polypropylene glycol, polytetramethylene glycol and the like in addition to compounds obtained by addition polymerization of alkylene oxide to polyhydric alcohol. As the polyhydric alcohol, glycerin, dipropylene glycol, trimethylolpropane and the like are used. As the alkylene oxide, ethylene oxide, propylene oxide or the like is used.

  Specifically, the polyether polyol is a triol obtained by addition polymerization of propylene oxide to glycerin, a triol obtained by addition polymerization of ethylene oxide, a diol obtained by addition polymerization of propylene oxide to dipropylene glycol, and an addition polymerization of ethylene oxide. Diols and the like. When addition polymerization of ethylene oxide is performed, the content is preferably 5 to 20% by mass. When using a polyether polyol, propylene oxide as the main component is preferable for forming the urethane skeleton of the foam, and a mixture of triol and diol is used as the polyether polyol to further adjust the urethane skeleton. Is preferred.

  The polyether polyol may be a polyether ester polyol. The polyether ester polyol is a compound obtained by reacting a polyoxyalkylene polyol with a polycarboxylic acid anhydride and a compound having a cyclic ether group. Examples of polyoxyalkylene polyols include polyethylene glycol, polypropylene glycol, and propylene oxide adducts of glycerin. Examples of polycarboxylic acid anhydrides include anhydrides such as succinic acid, adipic acid, and phthalic acid. Examples of the compound having a cyclic ether group (alkylene oxide) include ethylene oxide and propylene oxide. The polyether polyol is preferable from the viewpoint that it has excellent reactivity with polyisocyanates and does not hydrolyze as compared with the polyester polyol.

  Polyester polyols include condensed polyester polyols obtained by reacting polycarboxylic acids such as adipic acid and phthalic acid with polyols such as ethylene glycol, propylene glycol and glycerin, as well as lactone polyester polyols and polycarbonate polyester polyols. Is used. The above polyols can change the functional group number and hydroxyl value of a hydroxyl group by adjusting the kind of raw material component, molecular weight, polymerization degree, condensation degree and the like.

  These polyols may be used alone or in admixture of two or more. The average number of functional groups for the hydroxyl groups of these polyols is not particularly limited, but is preferably 2-6, more preferably 3-4. Moreover, the hydroxyl value of polyols is not particularly limited, but is usually 15 to 2000, preferably 20 to 1000, and more preferably 30 to 500.

  The foam material preferably contains a crosslinking agent in order to form a crosslinked structure in the foam to increase the strength. In order to improve the function, such a crosslinking agent preferably has a hydroxyl group having three or more functional groups, and examples thereof include triols such as glycerin, trimethylolpropane and triethanolamine, and tetraols such as pentaerythritol. Although content of this crosslinking agent is not specifically limited, Preferably it is 1-10 mass parts per 100 mass parts of polyols, More preferably, it is 3-7 mass parts. When content of a crosslinking agent is less than 1 mass part, the crosslinking density of a foam becomes low and mechanical properties, such as compressive strength, fall. On the other hand, when it exceeds 10 mass parts, the crosslinking density of a foam becomes high, the connectivity of a cell falls, and the sound absorption characteristic tends to deteriorate.

  Next, polyisocyanates based on modified 4,4'-diphenylmethane diisocyanate (4,4'-MDI) are used to make the skeleton structure of the foam dense. When 4,4'-MDI is not a main component, the mechanical properties as a hard foam are not exhibited. Modified 4,4'-MDI (also referred to simply as MDI or monomeric MDI) means urethane-modified MDI and carbodiimide-modified MDI. Urethane-modified MDI is obtained by reacting MDI with diol, triol or the like, and carbodiimide-modified MDI is obtained by reacting MDI with carbodiimide such as dicyclohexylcarbodiimide. Examples of the MDI include pure MDI such as 2,4'-MDI and 2,2'-MDI, and crude MDI. Among the modified MDIs, urethane-modified MDI is preferable in order to reinforce the urethane skeleton of the rigid polyurethane foam.

  The polyisocyanates have a modified MDI as a main component, and the modified MDI alone or a modified MDI can be used as a main component and other polyisocyanates can be mixed and used. Other polyisocyanates are not particularly limited, and various aromatic, aliphatic and alicyclic polyisocyanates are used, for example. Examples of the aromatic polyisocyanate include tolylene diisocyanate (TDI), 1,5-naphthalene diisocyanate (NDI), paraphenylene diisocyanate, and m-xylene diisocyanate. Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate. Examples of the alicyclic polyisocyanate include isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate, and hydrogenated MDI.

  The content of these polyisocyanates is appropriately adjusted by a predetermined isocyanate index (isocyanate index). Here, the isocyanate index represents a ratio of the number of equivalents of isocyanate groups of polyisocyanates to the number of equivalents of active hydrogen groups such as polyols, water as a foaming agent, and a foam breaker. The isocyanate index is usually 80 to 150, preferably 100 to 120. When the isocyanate index is less than 80, foaming does not proceed smoothly, and the foam may be cracked or the foam may be partially deformed. On the other hand, when the isocyanate index exceeds 150, the crosslinking density of the foam increases and the cell tends to become closed cells, making it difficult to obtain a rigid polyurethane foam having an open cell structure.

  As the foaming agent, water, alkylene chlorides such as methylene chloride and ethylene chloride, isopentane, and the like are used, and water is preferable from the viewpoint of foaming action and ease of handling. These may be used alone or in combination of two or more. Although content of this foaming agent is not specifically limited, Preferably it is 1-10 mass parts per 100 mass parts of polyol, More preferably, it is 2-6 mass parts. When the content of the foaming agent is less than 1 part by mass, foaming is not sufficiently performed and a good foam cannot be obtained. On the other hand, when the content of the foaming agent exceeds 10 parts by mass, foaming becomes excessive and a hard polyurethane foam excellent in physical properties such as hardness and compressive strength cannot be obtained.

  Examples of the catalyst include an amine catalyst and a metal catalyst. Examples of the amine catalyst include triethylenediamine, tetramethylguanidine, N, N, N′N′-tetramethylhexane-1,6diamine, and bis (dimethylaminoethyl) ether. Examples of the metal catalyst include potassium octylate, dibutyltin dilaurate, lead naphthenate, and zinc neodecanoate. These may be used alone or in combination of two or more. Moreover, when using together, you may combine any, such as an amine catalyst and a metal catalyst.

  Although the content of this catalyst is not particularly limited, it is preferably 0.1 to 8 parts by mass, more preferably 1 to 5 parts by mass per 100 parts by mass of polyols. When the content of the catalyst is less than 0.1 parts by mass, the urethanization reaction or the like is not sufficiently accelerated, and the production efficiency of the foam is lowered, which is not preferable. On the other hand, when the amount exceeds 8 parts by mass, the progress of the urethanization reaction becomes so fast that side reactions are liable to occur.

  Next, the foam breaker is a substance that inhibits foam formation during foaming, increases the cell diameter, or promotes the open cell structure of the foam by communicating the cells. This foam-breaking agent is obtained by mixing propylene oxide and ethylene oxide in triol, and addition-polymerizing a mixture having an ethylene oxide content of 60% by mass or more in the mixture. As the triol, glycerin, trimethylolpropane, triethanolamine or the like is used. The content of ethylene oxide is 60% by mass or more in the mixture, but preferably 90 to 95% by mass. When the content of ethylene oxide is less than 60% by mass, the hydrophilicity of the addition polymer becomes low and the function as a foam breaker cannot be achieved. The triol content is preferably 1 to 5% by mass. The content of propylene oxide is preferably 3 to 40% by mass.

  The content of the foam breaker is preferably 3 to 10 parts by mass per 100 parts by mass of the polyols in order to sufficiently exhibit its function. When this content is less than 3 parts by mass, the foam breaking action at the time of foaming of the foam raw material is not sufficiently exhibited, and the connectivity of the cell is lowered. On the other hand, when it exceeds 10 parts by mass, the bubble breaking action becomes stronger, the cell diameter becomes larger, the cell connectivity becomes higher, and the mechanical properties such as compressive strength tend to decrease.

  In addition, the raw material of a foam can contain an antifoamer and the cell diameter of a foam can be adjusted with the content. As the antifoaming agent, silicone-based, oil-based, fatty acid-based, fatty acid ester-based, phosphate ester-based compounds and the like are used. Furthermore, the foam raw material may contain components such as foam stabilizers, fillers, plasticizers, antioxidants, ultraviolet absorbers, anti-aging agents, flame retardants, stabilizers, and colorants as necessary. Can do.

  Then, the polyurethane foam is made to react and foam and cure to produce a rigid polyurethane foam, but the reaction at that time is complicated, and basically the following reaction is the main component. Yes. That is, addition polymerization reaction of polyols and polyisocyanates (urethanization reaction, resinification reaction), foaming (foaming) reaction of polyisocyanates with water as a blowing agent, and reaction products of these and polyisocyanates And crosslinking (curing) reaction. When producing a polyurethane foam, a one-shot method in which a polyol and a polyisocyanate are directly reacted or a polyol and a polyisocyanate are reacted in advance to obtain a prepolymer having an isocyanate group at the terminal, Any of the prepolymer methods in which polyols are reacted therewith can be employed. Polyurethane foam is foamed and cured in the mold by injecting the polyurethane foam raw material (reaction mixture) into the slab foam obtained by foaming and curing at room temperature and atmospheric pressure, and in the mold, and clamping the mold. It may be produced by any method of the molded foam obtained.

  The polyurethane foam produced as described above is a rigid polyurethane foam and has an open cell structure. Here, the open cell structure means a structure in which foam cells communicate with each other. Specifically, the closed cell ratio measured in accordance with the air pycnometer method of ASTM D 2856 is 5% or less. Means that. The closed cell ratio is preferably 3% or less, more preferably 1% or less, and most preferably substantially 0%. The lower the closed cell rate, in other words, the higher the open cell rate, the better the sound absorption characteristics of the rigid polyurethane foam.

The density of the foam is not particularly limited, but the apparent density measured according to JIS A 9511 is preferably 100 to 250 kg / m ³ , more preferably 150 to 200 kg / m ³ . When this apparent density is less than 100 kg / m ³ , the foam cannot have sufficient hardness as a hard foam. On the other hand, when the apparent density exceeds 250 kg / m ³ , the air flow rate of the foam decreases, and sufficient sound absorption characteristics cannot be exhibited.

Moreover, the compressive strength used as the scale of the hardness of a foam is not specifically limited, However, The compressive strength measured based on JISA9511 becomes like this. Preferably it is 10-100 N / cm < ² >, More preferably, it is 30-60 N / cm < ² >. It is. When this compressive strength is less than 10 N / cm ² , the foam has insufficient hardness and tends to have insufficient mechanical strength (resin strength). On the other hand, when it exceeds 100 N / cm ² , the foam becomes too hard, and the properties as the foam may be impaired, and the connectivity of the cells tends to decrease.

  Furthermore, the air permeability of the foam is preferably 10 (l / min) or more, more preferably 10 to 25 (l / min) as a value measured in accordance with JIS K 6401. When the air flow rate is less than 10 (l / min), the air flow rate is insufficient, and the sound absorption characteristics of the foam based on the air permeability are deteriorated.

  Moreover, the average cell diameter of a foam becomes like this. Preferably it is 0.5-10 mm, More preferably, it is 1-3 mm. When this average cell diameter is less than 0.5 mm, the foam cannot exhibit sufficient sound absorption characteristics due to a decrease in cell connectivity. On the other hand, when the average cell diameter exceeds 10 mm, the foam cannot express mechanical properties such as sufficient hardness.

  The above rigid polyurethane foam has an open cell structure and is excellent in sound absorption characteristics, and therefore is suitably used as a sound absorbing material. The shape of the sound absorbing material is not particularly limited and can be a desired shape depending on the application, but the thickness is usually 5 to 100 mm, preferably 8 to 50 mm, more preferably 10 to 30 mm. When this thickness is less than 5 mm, the normal incident sound absorption coefficient becomes small, and sufficient sound absorption characteristics may not be obtained. Further, this sound absorbing material can be used as a sound absorbing product by laminating with other base materials. Examples of such a substrate include metals such as iron, stainless steel, and aluminum, resins, and wood. The method for laminating the sound absorbing material and the substrate is not particularly limited, and a general method is adopted. Examples thereof include a method of directly applying a foam raw material to a base material and foaming, and a method of joining the base material and a sound absorbing material with an adhesive or the like.

  The sound absorbing material can have a sufficient sound absorbing characteristic in a wide sound range of 800 to 5000 Hz, particularly 1000 to 3000 Hz, and is useful in a wide noise range. In addition, this sound absorbing material may have a maximum value of normal incident sound absorption coefficient measured in accordance with JIS A 1405 in a sound range of 1000 to 3000 Hz, particularly 1500 to 3000 Hz. In that case, the maximum value of the normal incidence sound absorption coefficient may be 80% or more, particularly 90% or more. Such a sound absorbing material can exhibit sufficient sound absorbing characteristics in a wide range of noise. In particular, it is possible to effectively absorb noise such as wind noise during vehicle travel. The sound range where the normal incident sound absorption coefficient is maximized can be adjusted by changing the thickness of the rigid polyurethane foam constituting the sound absorbing material, the air flow rate, and the like.

  Now, to explain the operation of the present embodiment, the foam breaker contained in the raw material of the foam is obtained by adding propylene oxide and ethylene oxide to triol, and adding a mixture having an ethylene oxide content of 60% by mass or more in the mixture. It is obtained by polymerization. Since this foam-breaking agent has high hydrophilicity based on ethylene oxide, the formation of cells is hindered during the foaming process of the foam material, and the formed cells have a large cell diameter and a strong tendency to be broken. As a result, the tendency for the formed cells to communicate is increased. At the same time, since the foam breaker has a plurality of hydroxyl groups, the hydroxyl groups react with the polyisocyanates, and the foam breaker forms part of the skeleton of the foam.

  On the other hand, polyisocyanates are mainly composed of urethane-modified or carbodiimide-modified MDI. For this reason, the urethane bond and carbodiimide bond of the modified MDI react with the isocyanate group of the polyisocyanate, and the crosslinking reaction proceeds. Therefore, the crosslinking density of the foam is increased, and a sufficient skeleton structure is formed as a rigid polyurethane foam. As a result, the rigid polyurethane foam can increase the air permeability while having sufficient mechanical properties.

The effects exhibited by the above embodiment will be described collectively below.
-In the manufacturing method of the rigid polyurethane foam which has an open cell structure of this embodiment, it uses combining specific polyisocyanate and a foam breaker. Polyisocyanates are mainly composed of modified diphenylmethane diisocyanate. The foam breaker is obtained by mixing propylene oxide and ethylene oxide with triol, and addition-polymerizing a mixture having an ethylene oxide content of 60% by mass or more in the mixture.

  For this reason, the hard polyurethane foam can have an open cell structure with good communication while having a sufficient skeleton structure. As a result, the rigid polyurethane foam has a small closed cell ratio, can increase the air flow rate, and can exhibit excellent sound absorption characteristics. And such a hard polyurethane foam can be easily manufactured by using the said specific foam breaker and polyisocyanate as a raw material.

-When the content of the foam breaker is 3 to 10 parts by mass per 100 parts by mass of the polyol, the effect of the foam breaker can be sufficiently exhibited.
-Since the modified diphenylmethane diisocyanate is urethane-modified diphenylmethane diisocyanate, the urethane skeleton of the foam can be made more satisfactory.

-By containing a trifunctional or higher functional cross-linking agent in the foam material, the cross-linked structure of the foam can be made dense, and physical properties such as compressive strength can be enhanced.
-By setting an isocyanate index to 100-120, a hard segment can fully be formed in polyurethane, and physical properties, such as hardness of a rigid polyurethane foam, and compressive strength, can be improved.

  As described above, since the hard polyurethane foam is excellent in sound absorption characteristics, it has sound absorption characteristics equivalent to or better than those of general soft polyurethane foam, and is used for interior materials such as automobiles such as ceilings. It can be suitably used as a sound-absorbing material in applications that require sound-absorbing properties such as a base material. In addition, since the maximum value of the normal incident sound absorption coefficient is in the sound range of 1000 to 3000 Hz, it is possible to effectively absorb noise such as wind noise when the vehicle is running, and the maximum normal incident sound absorption coefficient is 80% or more. Therefore, it is possible to effectively absorb noise in the sound range near the maximum value.

Hereinafter, the embodiment will be described more specifically with reference to examples and comparative examples.
(Examples 1-7 and Comparative Examples 1-3)
The raw materials of the polyurethane foam in each Example and Comparative Example are shown below, and their compositions are shown in Tables 1 and 2. And each component except polyisocyanate was first stirred and mixed using the hand mixer. Thereafter, polyisocyanates are blended according to the predetermined isocyanate index shown in Tables 1 and 2, 200 g of the mixture is put into a foaming container (length 150 mm, width 150 mm and height 150 mm), and reacted at room temperature and normal pressure. Foaming and curing were carried out to produce rigid polyurethane foams of the examples and comparative examples.

Here, Comparative Example 1 is an example corresponding to Example 1 described in Patent Document 1 of the related art, which does not use a foam breaker and uses polymeric MDI as a polyisocyanate instead of modified MDI. is there. Comparative Example 2 is an example in which polymeric MDI is used as polyisocyanate instead of modified MDI. Comparative Example 3 is an example using a low hydrophilicity foam breaker as the foam breaker.
(Raw material of polyurethane foam)
(Polyols)
Polyether polyol A: A polyether polyol obtained by addition polymerization of 83% by mass of propylene oxide and 15% by mass of ethylene oxide to 2% by mass of glycerin.

Polyether polyol B: A polyether polyol obtained by addition polymerization of 80% by mass of propylene oxide and 19% by mass of ethylene oxide to 1% by mass of dipropylene glycol.
(Foam breaker)
Defoamer 1: A defoamer comprising a polyol obtained by addition polymerization of 2% by mass of glycerin with 5% by mass of propylene oxide and 93% by mass of ethylene oxide.

Foam breaker 2: A foam breaker comprising a polyol obtained by addition polymerization of 33% by mass of propylene oxide and 65% by mass of ethylene oxide to 2% by mass of glycerin.
Defoaming agent 3: A defoaming agent comprising a polyol obtained by addition polymerization of 53% by mass of propylene oxide and 45% by mass of ethylene oxide with 2% by mass of glycerin.
(Crosslinking agent)
Glycerin (polyisocyanates)
Polyisocyanate a: Urethane-modified MDI {Modification rate 45% by mass (MDI content 55% by mass), Isocyanate group content 23% by mass}
Polyisocyanate b: Urethane-modified MDI {Modification rate 35% by mass (MDI content 65% by mass), Isocyanate group content 26% by mass}
Polyisocyanate c: Monomeric MDI
Polyisocyanate d: Polymeric MDI
(catalyst)
Potassium octylate: Product name Dabco K-15 manufactured by Air Products Japan Co., Ltd.

Triethylenediamine: manufactured by Kao Corporation, trade name Kao Raiser No. 31.
Bis (dimethylaminoethyl) ether (foaming agent)
Water (ion exchange water)
(Defoamer)
Silicone antifoaming agent: Toray Dow Corning Silicone Co., Ltd., trade name SH200.

About the rigid polyurethane foam obtained as mentioned above, the density, the compressive strength, the average cell diameter, the closed cell rate, the air flow rate and the normal incidence sound absorption coefficient were measured by the methods described below. The results are shown in Tables 1 and 2.
(density)
The density (kg / m ³ ) was measured according to JIS A 9511.
(Compressive strength)
The compressive strength (N / cm ² ) was measured according to JIS A 9511.
(Average cell diameter)
The cell diameter of a predetermined number of cells in each foam was measured with a microscope, and the average value of the measured values was taken as the average cell diameter.
(Closed cell rate)
The closed cell ratio (%) was measured according to ASTM D 2856 (air pycnometer method).
(Airflow)
The air flow (l / min) was measured according to JIS L 1096.
(Normal incidence sound absorption coefficient)
The normal incident sound absorption coefficient (%) was measured in accordance with JIS A 1405. That is, a specimen of rigid polyurethane foam (for low frequency measurement; diameter 100 mm, thickness 10 mm, for high frequency measurement; diameter 30 mm, thickness 10 mm) was prepared, and the normal incident sound absorption coefficient for the 1/3 octave band frequency. Was measured by a method defined in JIS A 1405, and the relationship between the frequency (Hz) and the normal incident sound absorption coefficient (%) was measured. The graph which shows the relationship between the obtained frequency and a normal incidence sound absorption coefficient was shown in FIG.1, FIG2 and FIG.3. Tables 1 and 2 show the maximum values of the normal incident sound absorption coefficient (%) in each example and comparative example.

表１に示した結果より、実施例１〜７においては、破泡剤として親水性の高い破泡剤１又は２を用い、ポリイソシアネート類として変性ＭＤＩであるポリイソシアネートａ又はｂを用いたことから、独立気泡率を０．１％以下に抑えることができ、通気量を１３．２〜２０．１（ｌ／ｍｉｎ）に増大させることができた。その結果、硬質発泡体の密度１８０ｋｇ／ｍ^３において、最大垂直入射吸音率を８１．０〜９５．５％まで高めることができ、吸音特性を向上させることができた。

From the results shown in Table 1, in Examples 1 to 7, a highly hydrophilic foam breaker 1 or 2 was used as the foam breaker, and polyisocyanate a or b, which is a modified MDI, was used as the polyisocyanate. Therefore, the closed cell ratio could be suppressed to 0.1% or less, and the air flow rate could be increased to 13.2 to 20.1 (l / min). As a result, when the density of the hard foam was 180 kg / m ³ , the maximum normal incident sound absorption coefficient could be increased to 81.0-95.5%, and the sound absorption characteristics could be improved.

  Furthermore, as shown in FIG. 1, in Examples 1-3, the improvement of the sound absorption characteristic was confirmed in the frequency range of 1200-5000 Hz, especially 1500-3200 Hz. In addition, as shown in FIG. 2, in Examples 4 to 7, it was confirmed that the sound absorption characteristics were improved in the frequency range of 1200 to 5000 Hz, particularly 1500 to 4000 Hz.

  On the other hand, as shown in Table 2, in Comparative Example 1, no foam-breaking agent was used, and polymerized MDI was used as the polyisocyanate instead of modified MDI. The rate reached 5.4%, and the air flow rate decreased to 0.3 (l / min). For this reason, the maximum value of the normal incident sound absorption coefficient was reduced to 68.4%, and the sound absorption characteristics were unsatisfactory. In Comparative Example 2, since the polymeric MDI was used as the polyisocyanate instead of the modified MDI, the air permeability was 8.8 (l / min), and the maximum value of the normal incident sound absorption coefficient was reduced to 69.3%. In Comparative Example 3, since a low hydrophilicity foam breaker was used as the foam breaker, the air flow rate was reduced to 11.4 (l / min) and the maximum value of the normal incident sound absorption coefficient was reduced to 76.5%. As shown in FIG. 3, in Comparative Example 1, the sound absorption characteristics were improved in the frequency range of 1300 to 5000 Hz, but the normal incident sound absorption coefficient was lower than that in Example 1.

In addition, this embodiment can also be changed and embodied as follows.
-A mixture of a plurality of modified MDIs can also be used.
-As a crosslinking agent, bifunctional ethylene glycol, diethylene glycol, propylene glycol, etc. can be used.

Further, the technical idea that can be grasped from the embodiment will be described below.
The said polyols are polyether polyols, and are a mixture of triol and diol, The rigid polyurethane foam having an open cell structure according to any one of claims 1 to 5, Production method. According to this manufacturing method, the urethane skeleton of the rigid polyurethane foam can be easily adjusted.

The graph which shows the relationship between a frequency and a normal incidence sound absorption coefficient about the rigid polyurethane foam of Examples 1-3. The graph which shows the relationship between a frequency and a normal incidence sound absorption coefficient about the rigid polyurethane foam of Examples 4-7. The graph which shows the relationship between a frequency and a normal incidence sound absorption coefficient about the rigid polyurethane foam of Comparative Examples 1-3.

Claims (5)

A method for producing a rigid polyurethane foam having an open-cell structure by reacting, foaming and curing raw materials of a polyurethane foam containing polyols, polyisocyanates, a catalyst, a foaming agent and a foam breaker,
The polyisocyanates are mainly composed of modified diphenylmethane diisocyanate, and the foam breaker is a mixture of propylene oxide and ethylene oxide in triol, and a mixture having an ethylene oxide content of 60% by mass or more is added to the mixture. A method for producing a rigid polyurethane foam having an open cell structure, which is obtained by polymerization. The method for producing a rigid polyurethane foam having an open-cell structure according to claim 1, wherein the content of the foam breaker is 3 to 10 parts by mass per 100 parts by mass of polyols. The method for producing a rigid polyurethane foam having an open cell structure according to claim 1 or 2, wherein the modified diphenylmethane diisocyanate is urethane-modified diphenylmethane diisocyanate. The method for producing a rigid polyurethane foam having an open-cell structure according to any one of claims 1 to 3, wherein the raw material contains a trifunctional or higher functional crosslinking agent. The isocyanate index which represents the equivalent ratio of the isocyanate groups of the polyisocyanates to the active hydrogen groups of the polyols, foaming agents and foam breakers as a percentage is 100 to 120. A method for producing a rigid polyurethane foam having an open-cell structure according to claim 1.

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