JP2012012519A - Thermosetting polyurethane composition, polyurethane molded article, and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyurethane molded article having excellent strength while having X-ray detectability.SOLUTION: The thermosetting polyurethane composition or others contains thermosetting polyurethane and X-ray contrast agent and is characterized in that the ratio of the X-ray contrast agent occupying in the total amount of the thermosetting polyurethane and the X-ray contrast agent is 2 mass% or more and 60 mass% or less.

Description

  The present invention relates to a thermosetting polyurethane composition, a polyurethane molded article formed from the thermosetting polyurethane composition, and a method for producing the polyurethane molded article.

  Conventionally, a molded article such as a medical tube is produced by using a polymer composition containing an X-ray contrast agent comprising an inorganic particle such as a metal or a metal oxide and containing an elastomer such as thermoplastic polyurethane as a base polymer. An X-ray detection property is imparted to shards and fragments thereof (see Patent Document 1 below).

While general rubber adjusts the characteristics of its composition by plasticizer components such as process oil, polyurethane is a long-chain polyol component used to form the hard segment or soft segment structure, It can be appropriately adjusted by selecting the short-chain polyol component and the polyisocyanate component, and it is easy to adjust the characteristics of the molded product without using a plasticizer.
Therefore, polyurethane molded articles such as tubes described in the following patent documents can be said to be suitable for medical use because they can exhibit desired characteristics while restricting the use of components that may bleed out. .

In addition, the provision of such X-ray detectability is required not only for medical purposes but also for food-related purposes.
If metal parts or their fragments are mixed in food, it is relatively easy to find them. However, if a molded product made of resin or rubber or its fragments are mixed in food, it is usually found. If, for example, the conveyor belt of a food conveyor is damaged and the broken pieces get mixed in with the food, the broken pieces are packaged with the food and reach the consumer's hand. May cause.
For this reason, efforts are made to provide X-ray detection for polymer molded products that make up equipment that is in direct or indirect contact with food, and to detect these contaminations in X-ray inspection before food shipment. Has been made.

On the other hand, so far no attention has been paid to the strength of the polymer molded product imparting X-ray detection properties, and no study has been conducted on a composition capable of producing a polymer molded product having excellent strength. Is the actual situation.
Therefore, it is difficult to obtain a molded article having excellent durability.

JP 2003-250901 A

  An object of the present invention is to solve the problems as described above, and to provide a composition capable of producing a molded article having excellent strength while containing an X-ray contrast agent, and having X-ray detectability. An object is to provide a molded article having excellent durability.

When a polyurethane molded article is to be obtained with a conventional thermoplastic polyurethane composition containing a thermoplastic polyurethane and an X-ray contrast agent, the thermoplastic polyurethane generally has a high softening temperature. An X-ray contrast agent is kneaded at a high temperature to produce pellets and the like, and this is extruded again at a high temperature.
In this regard, the present inventors have intensively studied paying attention to the above problems, and it is predicted that the physical properties of the thermoplastic polyurethane will be deteriorated to some extent in the process in which shear stress at high temperature such as kneading and extrusion is applied. Unlike the case of mixing inorganic particles such as glass powder and sand particles, inorganic particles composed of a metal having a relatively large atomic number, an oxide of the metal, or a salt thereof, which is generally used as an X-ray contrast agent. When kneading at high temperature to disperse in thermoplastic polyurethane, or when extruding the mixture, it was found that the strength inherent in thermoplastic polyurethane was lowered unexpectedly. The present invention has been completed.

  That is, the present invention includes a thermosetting polyurethane and an X-ray contrast agent, and the X-ray contrast agent occupies a total amount of the thermosetting polyurethane and the X-ray contrast agent in order to solve the problems. A thermosetting polyurethane composition characterized in that the ratio is 2% by mass or more and 60% by mass or less is provided.

  The present invention also includes a thermosetting polyurethane and an X-ray contrast agent, and the ratio of the X-ray contrast agent in the total amount of the thermosetting polyurethane and the X-ray contrast agent is 2% by mass or more and 60%. Provided is a polyurethane molded product characterized in that a thermosetting polyurethane composition having a mass% or less is at least partially formed from a thermoset.

  Furthermore, the present invention contains a thermosetting polyurethane and an X-ray contrast agent, and the proportion of the X-ray contrast agent in the total amount of the thermosetting polyurethane and the X-ray contrast agent is 2% by mass or more and 60%. Provided is a method for producing a polyurethane molded product, comprising producing a thermosetting polyurethane composition having a mass% or less and thermosetting the thermosetting polyurethane composition to produce a polyurethane molded product.

According to the present invention, since the X-ray contrast agent is contained in the thermosetting polyurethane resin composition, it is necessary to perform kneading at a high temperature as in the case where thermoplastic polyurethane is used as the base polymer. In addition, the X-ray contrast agent can be dispersed in the thermosetting polyurethane at a temperature near room temperature.
Further, when producing a polyurethane molded product, it is possible to employ a method in which a thermosetting polyurethane resin composition is thermoset by being cast into a mold without performing an extrusion process at a high temperature. .
That is, according to the present invention, a molded product can be obtained without performing a process in which shear stress is applied at a high temperature.
Furthermore, according to the present invention, since the X-ray contrast agent is contained in a proportion suitable for X-ray detection, a polyurethane molded product having excellent strength while having X-ray detection can be obtained.

The side view (a) which shows the structure of a centrifugal molding machine, and X-X 'sectional view (b). A photograph showing an evaluation of X-ray detectability (X-ray transmission photograph: round shadow is rice cracker, white square object is test piece).

In the embodiment of the present invention, first, a thermosetting polyurethane composition constituting a polyurethane molded product (hereinafter also simply referred to as “molded product”) will be described.
The thermosetting polyurethane composition according to the present embodiment contains a thermosetting polyurethane and an X-ray contrast agent, and the X-ray contrast agent includes the thermosetting polyurethane and the X-ray contrast agent. It is contained so that the proportion of the total amount is 2% by mass or more and 60% by mass or less.
That is, the thermosetting polyurethane composition contains the thermosetting polyurethane and the X-ray contrast agent so as to have a mass ratio of 40:60 to 98: 2.
In this embodiment, the thermosetting polyurethane which is the main component of the thermosetting polyurethane composition is composed of a polyol component, a polyisocyanate component, and a crosslinking agent component.

Examples of the polyol component include polyether polyols such as polyoxytetramethylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, and polybutylene glycol; polycarbonate diol, neopentyl glycol, polyethylene adipate ester, polyethylene butylene adipate ester, poly Examples thereof include polyester polyols such as butylene adipate ester and caprolactone ester diol, and these may be used alone or in combination of two or more.
Among these, it is preferable to employ a polyester polyol, and it is particularly preferable to employ a caprolactone ester diol.

The reason why such a polyester thermosetting polyurethane is preferable is that the polyester thermosetting polyurethane is superior in oil resistance and heat resistance as compared to other polyether thermosetting polyurethanes.
In particular, it is preferable to use a polyester-based thermosetting polyurethane containing a caprolactone ester diol because the lactone-based one is more resistant to abrasion and resistance than other adipates and aromatic ones. It is because it is excellent in ultraviolet and water resistance.
In other words, in food-related applications where the removal of foreign matter is strongly required, the peripheral equipment is often exposed to UV sterilization light or is exposed to water. It is preferable to employ a lactone polyester thermosetting polyurethane in that the curable polyurethane composition can be constituted.

Examples of the polyisocyanate component include aliphatic isocyanate, alicyclic isocyanate, and aromatic isocyanate.
Examples of the aliphatic isocyanate include aliphatic diisocyanates having 6 to 10 carbon atoms.
Specific examples include 1,6-hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, and the like.
Moreover, the isocyanurate body of hexamethylene diisocyanate and isophorone diisocyanate, the biuret body, the modified body of an adduct body, etc. can be mentioned.
Examples of the alicyclic isocyanate include alicyclic diisocyanates such as isophorone diisocyanate (IPDI), 4,4′-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, norbornane diisocyanate (NBDI), and the like.
Examples of the aromatic isocyanate include tolylene diisocyanate (TDI), phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate, xylylene diisocyanate (XDI), carbodiimide-modified MDI, and the like. Can be mentioned.
These may be used alone or in combination of two or more.

Examples of the crosslinking agent component include low-molecular diols such as ethylene glycol, 1,4-butanediol, diethylene glycol, trimethylolpropane, 1,6-hexanediol, and neopentyl glycol; ethylenediamine, hexamethylenediamine, isophoronediamine, and the like. The diamine etc. can be mentioned.
These may be used alone or in combination of two or more.

On the other hand, examples of the X-ray contrast agent include barium compounds such as barium sulfate; bismuth compounds such as bismuth nitrate, bismuth subnitrate, bismuth trioxide, bismuth subcarbonate, bismuth oxychloride, and bismuth tungstate; Fine particles made of tungsten compounds such as tungsten oxide, tungsten dioxide, and tungsten trioxide can be given.
Further, metal particles such as tungsten, molybdenum, tin, tantalum, rhenium, platinum, gold and silver can be used as the X-ray contrast agent.
These may be used alone or in combination of two or more.
Among these, it is preferable to employ particles made of any of barium sulfate, bismuth subnitrate, bismuth trioxide, tungsten or oxides thereof (tungsten monoxide, tungsten dioxide, tungsten trioxide).
These are preferable in that they have excellent X-ray detectability because of the large number of bismuth atoms contained.

In addition, since the X-ray contrast agent is mixed with a thermosetting polyurethane in a liquid state before curing as will be described later, it is preferable that the average particle diameter is 1 μm to 20 μm in consideration of dispersibility.
Furthermore, in order to improve dispersibility, surface treatment such as fatty acid treatment and coupling agent treatment may be performed.

  The ratio of the thermosetting polyurethane and the X-ray contrast agent in the thermosetting polyurethane composition in the present embodiment is 40:60 to 98: 2, because the X-ray contrast agent is below the lower limit, It becomes difficult to give sufficient X-ray detectability to a polyurethane molded product obtained by curing the thermosetting polyurethane composition, and even if it exceeds the upper limit, the X-ray detectability is further improved. This is because not only is it difficult to achieve this, but also the strength of the polyurethane molded product may be lowered due to the inclusion of an excessive X-ray contrast medium.

That is, when the X-ray contrast medium is contained exceeding the upper limit (60% by mass), for example, when this molded product is used as a component such as a food conveyor belt conveyor, the fragments are detected by X-rays. Although it is easy, the excessive blending of the X-ray contrast agent may reduce the tear strength of the molded product and easily cause breakage, which may be counterproductive for the purpose of preventing food contamination. Have.
From such a viewpoint, the content of the X-ray contrast agent is preferably 55% by mass or less, and particularly preferably 30% by mass or less.

In addition to the thermosetting polyurethane and the X-ray contrast agent, various additives can be added to the thermosetting polyurethane composition according to the present embodiment.
For example, additives such as antibacterial agents, antioxidants, antistatic agents, flame retardants, ultraviolet absorbers, stabilizers and pigments can be added.

However, if the proportion of the X-ray contrast agent or the proportion of the thermosetting polyurethane in the entire thermosetting polyurethane composition is reduced by other components, problems may occur in X-ray detectability or the physical properties of the polyurethane molded product may be reduced. May cause problems.
Therefore, even when such other components are contained, the proportion of the X-ray contrast agent in the entire thermosetting polyurethane composition is preferably 2% by mass to 60% by mass. The ratio is preferably 96% to 38% by mass.
That is, with respect to the other components, although it depends on the type, it is preferable that the proportion of the entire thermosetting polyurethane composition is about 2% by mass or less.

Such a thermosetting polyurethane composition is usually produced immediately before formation of a molded article using a general dispersion apparatus.
For example, when molding a polyurethane molded product, the polyol component, the crosslinking agent component, the X-ray contrast agent, and the polyisocyanate component previously mixed with the additive according to circumstances and the polyisocyanate component are poured into a mold. It can be produced in the course of a so-called one-shot molding method of mixing in a casting apparatus for molding.
Moreover, as a polyisocyanate component, a pseudo-prepolymer or a complete prepolymer containing a free isocyanate is prepared, and a polyol component and an X-ray contrast agent are mixed with the polyisocyanate component to prepare a thermosetting polyurethane composition. Also good.

If the content of the X-ray contrast agent is large, mixing all materials at once to produce a thermosetting polyurethane composition takes time until uniform mixing and the curing reaction proceeds. Or the moisture in the air is taken in and reacts with the isocyanate group of the isocyanate component, and the isocyanate group that should react with the active hydrogen of the polyol component may be lost.
For this reason, when the content of the X-ray contrast agent increases, a part or all of the X-ray contrast agent is mixed with the polyol component in advance to prepare a mixture, The thermosetting polyurethane composition is preferably prepared by a method of mixing the polyisocyanate component.
In terms of reducing the risk of deactivating isocyanate groups, the X-ray contrast agent is mixed with the polyol component in advance, regardless of the X-ray contrast agent content, and then mixed with the polyisocyanate component. It is preferable to do.

Moreover, it is preferable to implement such a technique using a pseudo prepolymer method.
To describe this in detail, in the complete prepolymer method, for example, a polyisocyanate is reacted with a polyol having a relatively high molecular weight of about 1000 to 3000 in such a manner that the number of functional groups is approximately equal. A long-chain polyisocyanate component having isocyanate groups at both ends is used as a main component, and a method in which a polyol component having a molecular weight lower than that of the prepolymer, for example, a molecular weight of about several hundreds, is employed. The reaction efficiency can be improved as compared with the case where the polyol component and the polyisocyanate component are reacted in the one-shot method without preparing such a prepolymer in advance.

  On the other hand, in the pseudo prepolymer method, only a part of a high molecular weight polyol to be reacted in a complete prepolymer is reacted with a polyisocyanate to prepare a prepolymer containing a free polyisocyanate (pseudoprepolymer), and the rest This is a method in which a polyol and a low molecular weight polyol are reacted with the pseudo-prepolymer, and the same effect as the complete prepolymer method can be expected. In addition, the polyol component for predispersing the X-ray contrast agent is compared with the complete prepolymer method. The advantage is that many can be secured.

In addition, by adopting the pseudo-prepolymer method, the pseudo-prepolymer is mixed after the X-ray contrast agent is dispersed to some extent in the polyol component, so the pseudo-prepolymer that is an isocyanate component is added. Therefore, the mixing time required until the X-ray contrast agent is dispersed in the entire thermosetting polyurethane composition can be shortened.
This makes it possible to improve the dispersibility of the X-ray contrast agent while preventing the deactivation of the isocyanate group in the case of using an X-ray contrast agent having a high aggregation property or when the content of the X-ray contrast agent is high. Can do.

In preparing such a composition, an advantageous effect is exhibited by using a thermosetting polyurethane as compared with a conventional method in which an X-ray contrast agent is dispersed in a thermoplastic polyurethane elastomer. .
That is, to disperse the X-ray contrast agent in the thermoplastic polyurethane elastomer, a kneader such as a twin screw extruder or a kneader is used. In such a case, for example, a hard oxide such as tungsten oxide is used. When the particles are used, the equipment is likely to be worn. As a result, the resulting composition contains wear powder as an impurity, and in some cases, it may be colored to impair the appearance of the polyurethane molded product.
On the other hand, when the X-ray contrast agent is dispersed in a liquid having a lower viscosity than that of a thermoplastic polyurethane elastomer in a hot melt state such as polyol, it can be uniformly dispersed without applying excessive shear stress (shear stress). Therefore, it is possible to suppress the possibility that the service life of the equipment may be shortened due to wear of the parts or the appearance of the polyurethane molded product may be impaired.

The thermosetting polyurethane composition according to this embodiment can obtain a polyurethane molded product in which the X-ray contrast agent is uniformly dispersed while preventing the shear stress as described above. It can suppress that the mechanical strength which a polyurethane has falls.
In general, when inorganic particles such as an X-ray contrast agent are contained in the thermosetting polyurethane, the toughness tends to be lowered. In particular, when an aggregate of inorganic particles is present, wear resistance, tear strength, There is a possibility that mechanical strength such as elongation and tensile strength is greatly reduced.
The thermosetting polyurethane composition according to this embodiment can prevent the formation of agglomerates because the dispersion of the X-ray contrast agent is good without the need for mixing and agitation in which strong shear is applied. A polyurethane molded article excellent in X-ray detectability and mechanical strength can be formed.

The detection performance by X-ray is substantially determined by the total amount of X-ray contrast agent existing in the X-ray transmission direction. For example, even a polyurethane molded product having a high X-ray contrast agent content is thin. If so, the same detectability as a thick polyurethane molded product having a low X-ray contrast agent content is exhibited.
From such a viewpoint, for example, in a polyurethane molded product that requires toughness such as wear resistance and tear strength, the content of the X-ray contrast agent on the surface thereof can be reduced compared to the internal content. It is preferable to form a polyurethane molded product in which the concentration distribution of the X-ray contrast agent is inclined from the surface toward the inside.

  For example, as a polyurethane molded article, a belt or a sheet that is highly versatile and easy to perform secondary processing can be cited as a suitable example. X-rays having the same X-ray detectability by producing a material having a high content rate or a material having a higher content of X-ray contrast agent in the central portion than both end portions (surface portion and back surface portion) in the thickness direction A polyurethane molded product having a higher strength than that of a polyurethane molded product in which the contrast agent is uniformly dispersed can be obtained.

Next, a method for producing such a polyurethane molded product will be described with reference to the drawings.
Here, an example in which polyurethane sheets having different X-ray contrast agent concentrations in the thickness direction using a centrifugal molding machine will be described.
First, the centrifugal molding machine will be described.

FIG. 1A is an explanatory diagram for explaining an example of a centrifugal molding machine, in which a state of a side surface of the centrifugal molding machine is partially cut out to show an internal state.
FIG. 1B is a sectional view taken along line XX ′ in FIG.
As shown in FIG. 1, the centrifugal molding machine 100 has a bottomed cylindrical shape with a closed end 111 on the side and an open end 112 on the other side, and the bottomed cylinder is placed in a horizontally placed state. A mold 110, a heater 120 for heating the mold 110, and a motor 130 for rotating the mold 110 around the cylindrical central axis are provided.

Further, in the centrifugal molding machine 100, the mold 110 and the heater 120 are accommodated in an overall substantially rectangular heat insulation chamber 150 having an opening / closing door 140.
The heat insulation chamber 150 is formed with a rectangular internal space large enough to accommodate the mold 110, and the mold 110 has its open end 112 facing the door 140 side. The heat insulation chamber 150 is accommodated.
The heater 120 is disposed so as to surround the mold 110 from all sides, and is provided in a state of being fixed to all six inner walls of the heat insulating chamber 150.

The heat insulation chamber 150 is provided with a through hole in the wall on the opposite side of the door 140, and the mold 110 is blocked by a shaft 160 extending from the outside of the heat insulation chamber 150 into the heat insulation chamber 150 through the through hole. It is pivotally supported on the end 111 side.
The shaft 160 is arranged coaxially with the central axis of the mold 110 and is fixed to the through hole using a mechanical seal.
A pulley 161 is attached to the shaft 160 outside the heat insulating chamber 150, and the pulley 161 and the motor of the shaft 160 are rotated so as to rotate as the pulley 132 attached to the rotating shaft 131 of the motor 130 rotates. A transmission belt 170 is stretched between 130 pulleys 132.

  That is, the centrifugal molding machine illustrated in FIG. 1 can open the opening / closing door 140 of the heat insulating chamber 150 and allow the liquid thermosetting polyurethane composition to flow into the mold 110 from the open end 112 side of the mold 110. At the same time, the mold 110 can be rotated around the central axis by driving the motor 130 while heating the thermosetting polyurethane composition introduced from the heater 120 together with the mold 110 from the outside. Yes.

A method for producing a sheet-like polyurethane molded product (polyurethane sheet) using the centrifugal molding machine 100 will be described.
First, a thermosetting polyurethane composition exhibiting fluidity by centrifugal force acting in the mold 110 at least during operation of the centrifugal molding machine 100 is produced by the pseudo prepolymer method as described above.

Specifically, in preparing a prepolymer, the number of isocyanate groups is reduced by reducing the amount of a polyol having a molecular weight of about 1000 to 3000 (hereinafter also referred to as “high molecular weight polyol”) compared to the case of the complete prepolymer method. A polyisocyanate containing the polyisocyanate and the above-described high molecular weight polyol is reacted so as to be in excess of hydrogen, and the excess polyisocyanate is liberated.
Subsequently, the reduced amount of the high molecular weight polyol, or the low molecular weight (less than 1000) polyol (hereinafter also referred to as “low molecular weight polyol”) and the high molecular weight polyol, which are reacted with the pseudoprepolymer later together with the high molecular weight polyol. When the X-ray contrast agent is mixed with the polyol component and the dispersibility of the X-ray contrast agent with respect to the polyol component is ensured to some extent, the pseudo prepolymer (polyisocyanate component) is mixed and thermosetting. A polyurethane is produced.

This thermosetting polyurethane composition is placed in the mold 110, and the mold 110 is rotated while being heated by the heater 120, whereby the thermosetting polyurethane composition is rotated with the rotation of the mold 110. A cylindrical polyurethane molded article is produced by spreading the thermosetting polyurethane composition along the inner peripheral surface and thermosetting the thermosetting polyurethane composition in this state.
From this cylindrical polyurethane molded product, a polyurethane sheet can be produced by cutting it into a desired shape.

In the production of the polyurethane sheet by such a centrifugal molding machine, the centrifugal force acting on the X-ray contrast agent is used to change the content of the X-ray contrast agent on the outer peripheral surface side of the cylindrical body from the inner peripheral surface side. Can also be increased.
The distribution state of the X-ray contrast agent in the thickness direction of the polyurethane sheet can be adjusted by controlling the specific gravity of the X-ray contrast agent and the rotational speed of the mold 110.
At this time, as the X-ray contrast agent, particles made of a material having a high specific gravity such as tungsten, an oxide thereof, or a bismuth compound are used, so that the distribution is sensitive to changes in the rotational speed of the mold 110. The situation can be changed, and the concentration change of the X-ray contrast agent in the thickness direction of the polyurethane sheet can be facilitated.
In addition, it is also possible to produce polyurethane sheets having different distribution situations by employing a plurality of types of X-ray contrast agents having different specific gravity.
For example, by adopting an X-ray contrast agent having a high specific gravity such as tungsten particles and a low specific gravity X-ray contrast agent having a smaller specific gravity than this, adjusting the number of revolutions at the time of centrifugal molding, the low specific gravity can be obtained. It is also possible to produce a polyurethane sheet by allowing the X-ray contrast medium to exist in a wide range from the inner side to the outer side in the thickness direction and the X-ray contrast medium having a high specific gravity to be present in a biased direction.

  This polyurethane sheet can be used as a single member of a sheet, or a side wall member of a transport conveyor device that transports an object to be inspected to an X-ray foreign matter detection device by being attached to the surface of another plate material, for example, By forming the side wall with the low X-ray contrast agent content side corresponding to the inner peripheral surface side of the cylindrical body facing inward, it is possible to suppress the occurrence of problems such as wear and chipping due to the collision of the inspection object.

In addition, before thermosetting the thermosetting polyurethane composition with a centrifugal molding machine, another heat containing the same or different thermosetting polyurethane as the thermosetting polyurethane composition and containing no X-ray contrast agent. The curable polyurethane composition is heat-cured with the centrifugal molding machine 100, and after the fluidity has been lost but the semi-cured state is not completely cured, an X-ray contrast medium is placed inside the curable polyurethane composition. The content of the X-ray contrast agent in the central portion in the thickness direction is greater than that on the inner peripheral surface side and the outer peripheral surface side by carrying out thermosetting by adding the thermosetting polyurethane composition contained therein and performing centrifugal molding again. A cylindrical polyurethane molded product can be produced.
Since such a polyurethane sheet has excellent strength on both the front and back surfaces, it is not necessary to consider whether the front and back surfaces are different from the strength surface, and can be used easily.

When centrifugal molding is used in this way, the concentration of the X-ray contrast medium varies depending on the location of the molded product, but in that case, in the portion where the concentration of the X-ray contrast medium is the highest. It is preferable that the ratio of the thermosetting polyurethane to the X-ray contrast medium is 40:60 to 98: 2.
In the present embodiment, a method using a centrifugal molding machine as described above is exemplified in that a higher-strength urethane molded product can be produced, but the method for producing a polyurethane molded product according to the present invention is as follows. The method is not limited to a method using a centrifugal molding machine, and a thermosetting polyurethane composition containing a thermosetting polyurethane and an X-ray contrast agent in a mass ratio of 40:60 to 98: 2 is used. If it does, the specific manufacturing method is not specifically limited.

Further, the form of the polyurethane molded product to be produced is not limited to the sheet, and the polyurethane molded product according to the present embodiment is intended for those having a three-dimensional structure and various forms.
For example, the thermosetting polyurethane composition is poured into a mold containing a core metal and thermoset to produce a food transport roller having an elastic layer made of a cured body of the thermosetting polyurethane composition. You can also.
Further, even technical matters not specifically exemplified above can adopt conventionally known technical matters as long as the effects of the present invention are not significantly impaired.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

(Production of polyurethane molded product 1)
A polyurethane sheet having a thickness of 1 mm was prepared according to the formulation shown in Table 1 below.
Specifically, except the thing of the comparative example 1, it produced as follows.
In a plastic container (capacity: 2 liters) with a screw cap, 1000 g of a mixture obtained by mixing “polyol 1”, “crosslinking agent” and “X-ray contrast agent” in Table 1 at a temperature of 70 ° C. was added and heated to 70 ° C. 600 g of zirconia beads having an average particle size of about 5 mm was put, and the container was set in a tumbler mixer (T2F type, manufactured by Shinmaru Enterprises Co., Ltd.) and stirred for 30 minutes.
The zirconia beads were removed from the resulting mixture and stored at a temperature of 70 ° C. for a while.
Next, the one heated to 100 ° C. and the one obtained by heating “Prepolymers 1 to 3” in Table 1 to 100 ° C. were stirred with a propeller while being careful not to entrain air, and obtained. The thermosetting polyurethane composition was placed in a mold of a centrifugal molding machine heated to 150 ° C., and the mold was rotated to perform centrifugal molding to produce a polyurethane molded product.
Specifically, a cylindrical cured body was obtained by thermosetting over 60 to 90 minutes, and this was post-cured in an oven at 110 ° C. for 12 to 24 hours.

  On the other hand, the thermoplastic polyurethane of Table 1 was melt kneaded at a temperature of 200 ° C. with an extrusion molding machine (manufactured by Tanabe Plastic Machinery Co., Ltd.), extruded from a die, and the polyurethane sheet of Comparative Example 1 having a thickness of 1.0 mm. Produced.

The polyurethane sheet thus obtained was evaluated as follows.
・ DIN wear:
It was carried out by the DIN abrasion test method specified in JIS K 6264.
However, the test piece was carried out with a sheet thickness of 1 mm, and the test surface was the inner surface in centrifugal molding.
・ Tear test:
A test using a B-shaped test piece having no notch defined in JIS K 7312 was performed.
However, the test piece thickness was 1 mm.

-X-ray detectability:
A test piece of 1 cm x 1 cm is cut out from each polyurethane sheet, and the presence of the test peel is recognized from above the packaged confectionery by X-rays under the packaged confectionery in which 74 g of rice cake is contained in an aluminum laminate bag. To see if it is possible.
These results are shown together in Table 1.

In addition, the photograph which shows a mode that X-ray detection property was evaluated about the test piece of the said Example 3 is shown in FIG. 2 (a round shadow is a rice cracker, and a white square object is a test piece).
This FIG. 2 shows an X-ray transmission image projected on an X-ray inspection apparatus. As can be seen from this figure, the urethane sheet of the present invention can clearly grasp its presence and detect X-rays. It turns out that it is excellent in property.

Also from the results of Table 1 and FIG. 2, when thermoplastic polyurethane is used (Comparative Example 1), the wear resistance is low and the strength is not sufficient, and the X-ray contrast agent is excessively reduced (Comparative Example 2). On the contrary, it can be seen that there is no problem in these intensities, but there is a problem in X-ray detection.
And according to this invention, it turns out that the polyurethane molded product which has the intensity | strength outstanding while having X-ray detection property can be obtained.

(Production of polyurethane molded product 2)
As shown in Table 2, a thermosetting polyurethane composition that does not contain an X-ray contrast agent is put in a centrifugal molding machine to produce a 0.5 mm-thick cylindrical body (first layer). Except that a thermosetting polyurethane composition containing an X-ray contrast agent was placed in a thickness of 0.5 mm (second layer) and subjected to centrifugal molding to produce a polyurethane sheet having a thickness of 1 mm. A polyurethane sheet was prepared in the same procedure as in 1 to 5, and evaluated in the same manner.
In addition, about DIN abrasion, evaluation was implemented with respect to the 1st layer which does not contain an X-ray contrast agent.
The results are shown in Table 2.

  From the results of Table 2, it can be seen that according to the present invention, it is possible to obtain a polyurethane molded article having excellent strength while having X-ray detectability.

100: Centrifugal molding machine, 110: Mold

Claims (17)

  It contains a thermosetting polyurethane and an X-ray contrast agent, and the ratio of the X-ray contrast agent in the total amount of the thermosetting polyurethane and the X-ray contrast agent is 2% by mass or more and 60% by mass or less. A thermosetting polyurethane composition characterized by the above.   The thermosetting polyurethane composition according to claim 1, wherein the X-ray contrast agent is a particle made of any one of barium sulfate, bismuth subnitrate, bismuth trioxide, tungsten, or an oxide thereof.   The thermosetting polyurethane composition according to claim 1 or 2, wherein the thermosetting polyurethane is a polyester thermosetting polyurethane.   The thermosetting polyurethane composition according to claim 3, wherein the polyester polyol constituting the polyester-based thermosetting polyurethane is a polycaprolactone polyol.   A heat containing a thermosetting polyurethane and an X-ray contrast agent, wherein the proportion of the X-ray contrast agent in the total amount of the thermosetting polyurethane and the X-ray contrast agent is 2% by mass or more and 60% by mass or less. A polyurethane molded product, characterized in that at least a part of a curable polyurethane composition is formed by heat curing.   The polyurethane molded article according to claim 5, wherein the X-ray contrast agent is a particle made of any one of barium sulfate, bismuth subnitrate, bismuth trioxide, tungsten, or an oxide thereof.   The polyurethane molded article according to claim 5 or 6, wherein the thermosetting polyurethane is a polyester thermosetting polyurethane.   The polyurethane molded article according to claim 7, wherein the polyester polyol constituting the polyester-based thermosetting polyurethane is a polycaprolactone polyol.   It is a sheet | seat or a belt, The polyurethane molded product of any one of Claims 5 thru | or 8.   A heat containing a thermosetting polyurethane and an X-ray contrast agent, wherein the proportion of the X-ray contrast agent in the total amount of the thermosetting polyurethane and the X-ray contrast agent is 2% by mass or more and 60% by mass or less. A method for producing a polyurethane molded product, comprising producing a curable polyurethane composition, and thermosetting the thermosetting polyurethane composition to produce a polyurethane molded product.   The method for producing a polyurethane molded article according to claim 10, wherein the X-ray contrast agent is a particle made of any one of barium sulfate, bismuth subnitrate, bismuth trioxide, tungsten, or an oxide thereof.   The method for producing a polyurethane molded product according to claim 10 or 11, wherein the thermosetting polyurethane is a polyester thermosetting polyurethane.   The method for producing a polyurethane molded product according to claim 12, wherein the polyester polyol constituting the polyester-based thermosetting polyurethane is polycaprolactone polyol.   A method in which the polyol component of the thermosetting polyurethane and the polyisocyanate component are mixed with the polyol component and the X-ray contrast agent to prepare a mixture, and then the mixture and the polyisocyanate component are mixed. The method for producing a polyurethane molded product according to any one of claims 10 to 13, wherein the thermosetting polyurethane composition is produced by the method.   The method for producing a polyurethane molded product according to claim 14, wherein the polyisocyanate component is a pseudo-prepolymer containing free polyisocyanate.   The thermosetting polyurethane composition having fluidity is prepared, the thermosetting polyurethane composition is subjected to centrifugal molding with a centrifugal molding machine and the thermosetting is performed, and the content of the X-ray contrast agent on the outer peripheral surface side is the inner circumference. The method for producing a polyurethane molded product according to any one of claims 10 to 15, wherein a cylindrical polyurethane molded product having a larger number than the surface side is produced.   Before thermosetting the thermosetting polyurethane composition with a centrifugal molding machine, the thermosetting polyurethane composition containing no X-ray contrast agent is centrifugally molded in the centrifugal molding machine to be semi-cured, By putting the thermosetting polyurethane composition containing the X-ray contrast agent inside the thermosetting polyurethane composition and performing centrifugal molding, the content of the X-ray contrast agent in the central portion in the thickness direction becomes the inner peripheral surface side and The manufacturing method of the polyurethane molded product of Claim 16 which produces more cylindrical polyurethane molded products than an outer peripheral surface side.