const web3 = new Web3();
web3.setProvider(new
web3.providers.HttpProvider("https://mainnet.infura.io/XXXXXX"));
var count = web3.eth.getTransactionCount(from_addr);
var contract =  web3.eth.contract(abi).at(contract_addr);

var data = contract.transfer.getData(to_addr, 10, {from: from_addr});
var gasPrice = web3.eth.gasPrice;
var gasLimit = 90000;

var rawTransaction = {
  "from": from_addr,
  "nonce": web3.toHex(count),
  "gasPrice": web3.toHex(gasPrice),
  "gasLimit": web3.toHex(gasLimit),
  "to": to_addr,
  "value": 0,
  "data": data,
  "chainId": 0x01
};

var privKey = new Buffer(priv_key, 'hex');
var tx = new Tx(rawTransaction);

tx.sign(privKey);
var serializedTx = tx.serialize();

web3.eth.sendRawTransaction('0x' + serializedTx.toString('hex'), function(err, hash) {
  if (!err)
      console.log(hash);
  else
      console.log(err);
});